Francisco Antonio Muñoz Muñoz - Academia.edu (original) (raw)

Papers by Francisco Antonio Muñoz Muñoz

Research paper thumbnail of Electrophysiological evidence of an early effect of sentence context in reading

Biological Psychology, 2004

Recognition Potential is an electrophysiological response of the brain that is sensitive to seman... more Recognition Potential is an electrophysiological response of the brain that is sensitive to semantic aspects of stimuli. According to its peak values (about 250 ms), Recognition Potential appears as a good candidate to reflect lexical selection processes. Consequently, Recognition Potential might be sensitive to contextual information during reading a sentence. In present study, the standard procedures to improve the visibility of Recognition Potential (Rapid Stream Stimulation paradigm) were used in a task in which sentence context was crucial. A parieto-occipital Recognition Potential was observed to peak about 264 ms after stimulus onset, followed by a centro-parietal N400 peaking at about 450 ms. Recognition Potential was affected by contextual information though, contrary to N400, presenting larger amplitude to contextually congruous words. These results support the assumption that Recognition Potential may reflect lexical selection processes, representing also evidence of context effects on ERP around 250 ms after stimulus onset during sentence reading.

Research paper thumbnail of Long-Term Olanzapine Treatment and P300 Parameters in Schizophrenia

Research paper thumbnail of An electrophysiological (ERP) component, the recognition potential, in the assessment of brain semantic networks in patients with schizophrenia

Schizophrenia Research, 2004

Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) i... more Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) in patients with schizophrenia. However, whether this abnormality consists of increased or decreased activation is unclear. Previous behavioral and electrophysiological (N400) data have failed to yield consistent evidence for clarifying this hypothesis. One of the eventrelated potentials (ERP) components (the recognition potential, RP), presumably reflecting activation of specific semantic networks involved in ThD, has not been used to studies of schizophrenia, and may add additional information to support or refute this hypothesis. In an initial experiment, RP amplitude was reduced in schizophrenic patients, but particularly in those with ThD. In a second experiment, in addition to reduced overall RP amplitude, concrete words were shown to have higher amplitudes than abstract words in both patients and controls, supporting a relative integrity of the lexicon in ThD patients. RP reduction suggests that a fewer number of networks' elements are activated when an incoming word is processed, thus supporting hypoactivation of the semantic networks as the basis for ThD. D Abstract Concrete Abstract Concrete Abstract Alarms

Research paper thumbnail of Semantic processing of open- and closed-class words: an event-related potentials study

Cognitive Brain Research, 2001

Previous research on open-and closed-class words has revealed the existence of several difference... more Previous research on open-and closed-class words has revealed the existence of several differences in the processing of these types of vocabulary. In this paper the processing of open-and closed-class words was compared by means of an early electrical brain response, recognition potential (RP), which indexes semantic processing and originates from basal extrastriate areas. The effects of word frequency on closed-class words were also investigated. For these purposes, open-and closed-class words, among other stimuli, were presented by means of the rapid stream stimulation procedure. Results showed that there were no significant differences when comparing the RP evoked by open-and closed-class words in the left hemisphere. However, in the right hemisphere this situation changed: the RP evoked by open-and closed-class words did differ. Moreover, there were no differences between the RP evoked by closed-class words and pseudowords. These patterns of results suggest that the semantic processing of closed-class words shares some aspects with the processing of open-class words, despite the existence of some differences. Thus, whereas the semantic processing of open-class words recruits brain areas of both hemispheres, the semantic processing of closed-class words is left-lateralized. A second purpose of this work is to study word-frequency effects on closed-class words. Our results show the insensitivity of closed-class words to word-frequency effects.

Research paper thumbnail of Electrophysiological evidence of a semantic system commonly accessed by animals and tools categories

Cognitive Brain Research, 2001

Some theoretical perspectives propose a semantic system in which categories are represented in di... more Some theoretical perspectives propose a semantic system in which categories are represented in different brain regions. Others assume that distinctions are based rather on differences in the demands placed by different categories on shared processing systems. In this study semantic categorization processes were investigated using the recognition potential (RP), an event-related brain response that reflects semantic processing, peaks at around 250 ms after stimulus onset and originates in areas subserving perceptual-semantic analyses. Results indicate that the RP shows some degree of sensitivity to categorization processes, but that categories assumed to differ markedly in their processing demands share, to a large extent, a common neural generator. This provides support for the non-categorical view on the organization of the semantic system, though introducing subtle variations, and suggesting the existence of a semantic subsystem specializing in the processing of perceptual-semantic features regardless of the semantic category involved.

Research paper thumbnail of Syntactic expectancy: an event-related potentials study

Neuroscience Letters, 2005

Although extensive work has been conducted in order to study expectancies about semantic informat... more Although extensive work has been conducted in order to study expectancies about semantic information, little effort has been dedicated to the study of the influence of expectancies in the processing of forthcoming syntactic information. The present study tries to examine the issue by presenting participants with grammatically correct sentences of two types. In the first type the critical word of the sentence belonged to the most expected word category type on the basis of the previous context (an article following a verb). In the second sentence type, the critical word was an unexpected but correct word category (an article following an adjective) when a verb is highly expected. Event-related potentials (ERPs) were measured to critical words in both sentence types. Brain waves evoked by the correct but syntactically unexpected word revealed the presence of a negativity with a central distribution around 300-500 ms after stimuli onset, an N400, that was absent in the case of syntactically expected words. No differences were present in previous time windows. These results support models that differentiate between the processing of expected and unexpected syntactic structures.

Research paper thumbnail of Studying semantics in the brain: the rapid stream stimulation paradigm

Brain Research Protocols, 2001

Event-related potentials (ERPs) provide information about the temporal course of cognitive proces... more Event-related potentials (ERPs) provide information about the temporal course of cognitive processes in the brain. They have proved to be a valuable tool in order to explore semantic aspects of word processing. However, to date, research in this field has been mostly concerned with the study of post-lexical features by means of the N400-paradigm. We introduce here the rapid stream stimulation paradigm, in which stimuli reflecting different levels of linguistic information are presented to subjects at a high rate of stimulation. The present protocol shows in detail how this paradigm can be applied. The application of the rapid stream stimulation paradigm evokes the recognition potential (RP), an ERP component that peaks at around 260 ms after stimuli onset and seems to be reflecting lexical selection processes. Results of studies that revealed the sensibility of the RP to visual-semantic aspects and the location of its neural generators within basal extrastriate areas are reported. Although some research has been conducted with the rapid stream stimulation paradigm much remains still to be done. Some of the possibilities that this paradigm offers are further discussed.

Research paper thumbnail of P300 amplitude as a possible correlate of frontal degeneration in schizophrenia

Schizophrenia Research, 2001

The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 compone... more The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 component of event-related electrical potentials (ERP) has been related to the different degree of damage to gray and white matter. This study explores the possible relationship between P300 amplitude and/or latency and the existence of degenerative processes in schizophrenia, by assessing its correlation with volume of sulcal CSF and duration of illness, as transversal indicators of neurodegeneration.Nineteen patients (14 males, 5 females) and 13 controls (6 males, 7 females) were studied with MRI and electrophysiological records (P300). The possible influence of sex and age at the time of the exploration was statistically controlled in both groups.The results show a significant negative correlation between P300 amplitude and prefrontal CSF volume in the patient group. A lower though still significant correlation was also found between P300 amplitude and duration of illness, whereas no correlation was found in the control group. These results support the hypothesis that P300 amplitude may be interpreted as a marker of neurodegeneration in schizophrenia.

Research paper thumbnail of Higher-order activity beyond the word level: Cortical dynamics of simple transitive sentence comprehension

Brain and Language, 2005

Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independe... more Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independent of transient responses to individual words, have been reported. However, this type of activity has scarcely been studied, and with only limited use of electrophysiological information, so that the brain areas in which these variations originate have not been clearly identified. To improve this state of affairs, a principal component analysis and a modern source analysis algorithm (LORETA) were applied to the slow activity underlying transitive sentence reading. Four components explained 97.3% of the variance. Of key interest was a slow variation that occurred throughout the entire sentence but peaked with the appearance of the verb. The main solution for this component was localized in prefrontal and temporal regions presumably involved in semantic sentence processing. This constitutes empirical evidence for cortical activity-related to semantic processes thought to be involved in thematic role assignment-developing throughout the sentence but presenting a conspicuous maximum with the appearance of the verb. This finding also highlights the central role of verb information in the understanding of transitive sentences. (M. Martín-Loeches). www.elsevier.com/locate/b&l Brain and Language 92 (2005) 332-348

Research paper thumbnail of Electrophysiological evidence of automatic early semantic processing

Brain and Language, 2004

This study investigates the automatic-controlled nature of early semantic processing by means of ... more This study investigates the automatic-controlled nature of early semantic processing by means of the Recognition Potential (RP), an event-related potential response that reflects lexical selection processes. For this purpose tasks differing in their processing requirements were used. Half of the participants performed a physical task involving a lower-upper case discrimination judgement (shallow processing requirements), whereas the other half carried out a semantic task, consisting in detecting animal names (deep processing requirements). Stimuli were identical in the two tasks. Reaction time measures revealed that the physical task was easier to perform than the semantic task. However, RP effects elicited by the physical and semantic tasks did not differ in either latency, amplitude, or topographic distribution. Thus, the results from the present study suggest that early semantic processing is automatically triggered whenever a linguistic stimulus enters the language processor.

Research paper thumbnail of Dorsolateral prefrontal cortex contribution to abnormalities of the P300 component of the event-related potential in schizophrenia

Psychiatry Research-neuroimaging, 2005

Abnormalities of the P300 component of the event-related potential are a common finding in schizo... more Abnormalities of the P300 component of the event-related potential are a common finding in schizophrenia. It seems possible that the dysfunction in the dorsolateral prefrontal (DLPF) region that has been reported in schizophrenia contributes to this finding. To explore this possibility, we calculated the relationship between, on the one hand, P300 latency and amplitude and, on the other hand, the degree of DLPF atrophy (as measured by magnetic resonance imaging) and metabolic activity during an attentional task (as measured by positron emission tomography). Seventeen schizophrenia patients with a brief duration of illness and minimal exposition to treatment and 25 healthy controls were studied. Patients exhibited significantly lower metabolic activity in the DLPF region, but they did not show cortical atrophy. P300 amplitude was also significantly reduced in the schizophrenia patients compared with the controls. Right DLPF region metabolic activity correlated significantly with P300 amplitude. This pattern remained after partialling out the influence of activity in the hippocampus, superior temporal gyrus and parietal lobe. It is therefore suggested that the prefrontal cortex could be implicated in the P300 amplitude reduction in schizophrenia. D

Research paper thumbnail of Similarities and differences between phrase structure and morphosyntactic violations in Spanish: An event-related potentials study

Language and Cognitive Processes, 2003

Event-related potentials (ERPs) were employed to compare word category and verb inflection violat... more Event-related potentials (ERPs) were employed to compare word category and verb inflection violations in Spanish. A similar frontal negativity was found between 250-400 ms for both violation types, suggesting that they equally disrupt initial syntactic analyses. Also, word category violations elicited a negativity at posterior electrodes larger than verb inflection anomalies and correct sentences within this time window, probably reflecting difficulties to semantically analyse phrase structure violations. Finally, a centroparietal positivity in the 500-700 ms interval was found for both error types. Both violations did not differ along the first half of this interval (500-600 ms), but larger effects for verb inflection violations were reported along Requests for reprints should be addressed to José A Hinojosa, Brain Mapping Unit,

Research paper thumbnail of The recognition potential during sentence presentation: stimulus probability, background stimuli, and SOA

International Journal of Psychophysiology, 2004

Recognition potential (RP) is an electrical brain response that has proved its usefulness for stu... more Recognition potential (RP) is an electrical brain response that has proved its usefulness for studying semantic processing of isolated words, and appears when subjects view meaningful stimuli embedded in a stream of background images at a high rate of presentation: the rapid stream stimulation paradigm (RSS). The present technical study is aimed at testing the validity of this procedure in the study of words within sentences. For this purpose, we varied word and background probability of appearance, the number of background stimuli preceding each word, and stimulus onset asynchrony. Probability did not have significant effects on RP, but it was found that a minimum number of two background stimuli preceding each word and a high rate (250 ms) of presentation are preferable for enhancing RP amplitude. The RSS paradigm would therefore improve the visibility-and, hence, refine the analysis-of a component that can nevertheless be obtained with more standard paradigms, such as rapid serial visual presentation, devoid of interspersed background stimuli.

Research paper thumbnail of The recognition potential and repetition effects

International Journal of Psychophysiology, 2002

The recognition potential RP is an electrical brain response peaking at 250 ms that appears when ... more The recognition potential RP is an electrical brain response peaking at 250 ms that appears when subjects view meaningful stimuli. Previous RP research was conducted in experimental conditions in which repetition effects could not be totally ruled out as influencing the generation of the RP response. The present study aims to elucidate whether repetition effects affect the topography and waveform of this component. For this purpose semantically correct, orthographically correct, strings of random letters, control and background stimuli were presented to 20 subjects following the rapid stream stimulation procedure and without repetition of any test stimulus. As previously, the RP showed its maximal amplitude at the PO7 electrode. It showed sensitivity to all levels of lexical processing, its response being maximal for semantically correct stimuli, and its topographical distribution was similar for all types of stimulus. Direct statistical comparisons with the data of a previous study where repetition effects could not be disregarded were performed, confirming the similarity between the results obtained in both experiments. The neural generators of the RP were placed again, as in previous studies, within the lingual gyrus. Although repetition effects have been reported to affect other semantic-related components such as the N400, they do not seem to affect either the topography or the waveform of the RP. ᮊ

Research paper thumbnail of The recognition potential in the study of formal thought disorder and abnormal semantic processing in schizophrenia

Schizophrenia Research, 2003

Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) i... more Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) in patients with schizophrenia. However, whether this abnormality consists of increased or decreased activation is unclear. Previous behavioral and electrophysiological (N400) data have failed to yield consistent evidence for clarifying this hypothesis. One of the eventrelated potentials (ERP) components (the recognition potential, RP), presumably reflecting activation of specific semantic networks involved in ThD, has not been used to studies of schizophrenia, and may add additional information to support or refute this hypothesis. In an initial experiment, RP amplitude was reduced in schizophrenic patients, but particularly in those with ThD. In a second experiment, in addition to reduced overall RP amplitude, concrete words were shown to have higher amplitudes than abstract words in both patients and controls, supporting a relative integrity of the lexicon in ThD patients. RP reduction suggests that a fewer number of networks' elements are activated when an incoming word is processed, thus supporting hypoactivation of the semantic networks as the basis for ThD. D Abstract Concrete Abstract Concrete Abstract Alarms

Research paper thumbnail of Electrophysiological evidence of an early effect of sentence context in reading

Biological Psychology, 2004

Recognition Potential is an electrophysiological response of the brain that is sensitive to seman... more Recognition Potential is an electrophysiological response of the brain that is sensitive to semantic aspects of stimuli. According to its peak values (about 250 ms), Recognition Potential appears as a good candidate to reflect lexical selection processes. Consequently, Recognition Potential might be sensitive to contextual information during reading a sentence. In present study, the standard procedures to improve the visibility of Recognition Potential (Rapid Stream Stimulation paradigm) were used in a task in which sentence context was crucial. A parieto-occipital Recognition Potential was observed to peak about 264 ms after stimulus onset, followed by a centro-parietal N400 peaking at about 450 ms. Recognition Potential was affected by contextual information though, contrary to N400, presenting larger amplitude to contextually congruous words. These results support the assumption that Recognition Potential may reflect lexical selection processes, representing also evidence of context effects on ERP around 250 ms after stimulus onset during sentence reading.

Research paper thumbnail of Long-Term Olanzapine Treatment and P300 Parameters in Schizophrenia

Research paper thumbnail of An electrophysiological (ERP) component, the recognition potential, in the assessment of brain semantic networks in patients with schizophrenia

Schizophrenia Research, 2004

Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) i... more Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) in patients with schizophrenia. However, whether this abnormality consists of increased or decreased activation is unclear. Previous behavioral and electrophysiological (N400) data have failed to yield consistent evidence for clarifying this hypothesis. One of the eventrelated potentials (ERP) components (the recognition potential, RP), presumably reflecting activation of specific semantic networks involved in ThD, has not been used to studies of schizophrenia, and may add additional information to support or refute this hypothesis. In an initial experiment, RP amplitude was reduced in schizophrenic patients, but particularly in those with ThD. In a second experiment, in addition to reduced overall RP amplitude, concrete words were shown to have higher amplitudes than abstract words in both patients and controls, supporting a relative integrity of the lexicon in ThD patients. RP reduction suggests that a fewer number of networks' elements are activated when an incoming word is processed, thus supporting hypoactivation of the semantic networks as the basis for ThD. D Abstract Concrete Abstract Concrete Abstract Alarms

Research paper thumbnail of Semantic processing of open- and closed-class words: an event-related potentials study

Cognitive Brain Research, 2001

Previous research on open-and closed-class words has revealed the existence of several difference... more Previous research on open-and closed-class words has revealed the existence of several differences in the processing of these types of vocabulary. In this paper the processing of open-and closed-class words was compared by means of an early electrical brain response, recognition potential (RP), which indexes semantic processing and originates from basal extrastriate areas. The effects of word frequency on closed-class words were also investigated. For these purposes, open-and closed-class words, among other stimuli, were presented by means of the rapid stream stimulation procedure. Results showed that there were no significant differences when comparing the RP evoked by open-and closed-class words in the left hemisphere. However, in the right hemisphere this situation changed: the RP evoked by open-and closed-class words did differ. Moreover, there were no differences between the RP evoked by closed-class words and pseudowords. These patterns of results suggest that the semantic processing of closed-class words shares some aspects with the processing of open-class words, despite the existence of some differences. Thus, whereas the semantic processing of open-class words recruits brain areas of both hemispheres, the semantic processing of closed-class words is left-lateralized. A second purpose of this work is to study word-frequency effects on closed-class words. Our results show the insensitivity of closed-class words to word-frequency effects.

Research paper thumbnail of Electrophysiological evidence of a semantic system commonly accessed by animals and tools categories

Cognitive Brain Research, 2001

Some theoretical perspectives propose a semantic system in which categories are represented in di... more Some theoretical perspectives propose a semantic system in which categories are represented in different brain regions. Others assume that distinctions are based rather on differences in the demands placed by different categories on shared processing systems. In this study semantic categorization processes were investigated using the recognition potential (RP), an event-related brain response that reflects semantic processing, peaks at around 250 ms after stimulus onset and originates in areas subserving perceptual-semantic analyses. Results indicate that the RP shows some degree of sensitivity to categorization processes, but that categories assumed to differ markedly in their processing demands share, to a large extent, a common neural generator. This provides support for the non-categorical view on the organization of the semantic system, though introducing subtle variations, and suggesting the existence of a semantic subsystem specializing in the processing of perceptual-semantic features regardless of the semantic category involved.

Research paper thumbnail of Syntactic expectancy: an event-related potentials study

Neuroscience Letters, 2005

Although extensive work has been conducted in order to study expectancies about semantic informat... more Although extensive work has been conducted in order to study expectancies about semantic information, little effort has been dedicated to the study of the influence of expectancies in the processing of forthcoming syntactic information. The present study tries to examine the issue by presenting participants with grammatically correct sentences of two types. In the first type the critical word of the sentence belonged to the most expected word category type on the basis of the previous context (an article following a verb). In the second sentence type, the critical word was an unexpected but correct word category (an article following an adjective) when a verb is highly expected. Event-related potentials (ERPs) were measured to critical words in both sentence types. Brain waves evoked by the correct but syntactically unexpected word revealed the presence of a negativity with a central distribution around 300-500 ms after stimuli onset, an N400, that was absent in the case of syntactically expected words. No differences were present in previous time windows. These results support models that differentiate between the processing of expected and unexpected syntactic structures.

Research paper thumbnail of Studying semantics in the brain: the rapid stream stimulation paradigm

Brain Research Protocols, 2001

Event-related potentials (ERPs) provide information about the temporal course of cognitive proces... more Event-related potentials (ERPs) provide information about the temporal course of cognitive processes in the brain. They have proved to be a valuable tool in order to explore semantic aspects of word processing. However, to date, research in this field has been mostly concerned with the study of post-lexical features by means of the N400-paradigm. We introduce here the rapid stream stimulation paradigm, in which stimuli reflecting different levels of linguistic information are presented to subjects at a high rate of stimulation. The present protocol shows in detail how this paradigm can be applied. The application of the rapid stream stimulation paradigm evokes the recognition potential (RP), an ERP component that peaks at around 260 ms after stimuli onset and seems to be reflecting lexical selection processes. Results of studies that revealed the sensibility of the RP to visual-semantic aspects and the location of its neural generators within basal extrastriate areas are reported. Although some research has been conducted with the rapid stream stimulation paradigm much remains still to be done. Some of the possibilities that this paradigm offers are further discussed.

Research paper thumbnail of P300 amplitude as a possible correlate of frontal degeneration in schizophrenia

Schizophrenia Research, 2001

The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 compone... more The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 component of event-related electrical potentials (ERP) has been related to the different degree of damage to gray and white matter. This study explores the possible relationship between P300 amplitude and/or latency and the existence of degenerative processes in schizophrenia, by assessing its correlation with volume of sulcal CSF and duration of illness, as transversal indicators of neurodegeneration.Nineteen patients (14 males, 5 females) and 13 controls (6 males, 7 females) were studied with MRI and electrophysiological records (P300). The possible influence of sex and age at the time of the exploration was statistically controlled in both groups.The results show a significant negative correlation between P300 amplitude and prefrontal CSF volume in the patient group. A lower though still significant correlation was also found between P300 amplitude and duration of illness, whereas no correlation was found in the control group. These results support the hypothesis that P300 amplitude may be interpreted as a marker of neurodegeneration in schizophrenia.

Research paper thumbnail of Higher-order activity beyond the word level: Cortical dynamics of simple transitive sentence comprehension

Brain and Language, 2005

Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independe... more Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independent of transient responses to individual words, have been reported. However, this type of activity has scarcely been studied, and with only limited use of electrophysiological information, so that the brain areas in which these variations originate have not been clearly identified. To improve this state of affairs, a principal component analysis and a modern source analysis algorithm (LORETA) were applied to the slow activity underlying transitive sentence reading. Four components explained 97.3% of the variance. Of key interest was a slow variation that occurred throughout the entire sentence but peaked with the appearance of the verb. The main solution for this component was localized in prefrontal and temporal regions presumably involved in semantic sentence processing. This constitutes empirical evidence for cortical activity-related to semantic processes thought to be involved in thematic role assignment-developing throughout the sentence but presenting a conspicuous maximum with the appearance of the verb. This finding also highlights the central role of verb information in the understanding of transitive sentences. (M. Martín-Loeches). www.elsevier.com/locate/b&l Brain and Language 92 (2005) 332-348

Research paper thumbnail of Electrophysiological evidence of automatic early semantic processing

Brain and Language, 2004

This study investigates the automatic-controlled nature of early semantic processing by means of ... more This study investigates the automatic-controlled nature of early semantic processing by means of the Recognition Potential (RP), an event-related potential response that reflects lexical selection processes. For this purpose tasks differing in their processing requirements were used. Half of the participants performed a physical task involving a lower-upper case discrimination judgement (shallow processing requirements), whereas the other half carried out a semantic task, consisting in detecting animal names (deep processing requirements). Stimuli were identical in the two tasks. Reaction time measures revealed that the physical task was easier to perform than the semantic task. However, RP effects elicited by the physical and semantic tasks did not differ in either latency, amplitude, or topographic distribution. Thus, the results from the present study suggest that early semantic processing is automatically triggered whenever a linguistic stimulus enters the language processor.

Research paper thumbnail of Dorsolateral prefrontal cortex contribution to abnormalities of the P300 component of the event-related potential in schizophrenia

Psychiatry Research-neuroimaging, 2005

Abnormalities of the P300 component of the event-related potential are a common finding in schizo... more Abnormalities of the P300 component of the event-related potential are a common finding in schizophrenia. It seems possible that the dysfunction in the dorsolateral prefrontal (DLPF) region that has been reported in schizophrenia contributes to this finding. To explore this possibility, we calculated the relationship between, on the one hand, P300 latency and amplitude and, on the other hand, the degree of DLPF atrophy (as measured by magnetic resonance imaging) and metabolic activity during an attentional task (as measured by positron emission tomography). Seventeen schizophrenia patients with a brief duration of illness and minimal exposition to treatment and 25 healthy controls were studied. Patients exhibited significantly lower metabolic activity in the DLPF region, but they did not show cortical atrophy. P300 amplitude was also significantly reduced in the schizophrenia patients compared with the controls. Right DLPF region metabolic activity correlated significantly with P300 amplitude. This pattern remained after partialling out the influence of activity in the hippocampus, superior temporal gyrus and parietal lobe. It is therefore suggested that the prefrontal cortex could be implicated in the P300 amplitude reduction in schizophrenia. D

Research paper thumbnail of Similarities and differences between phrase structure and morphosyntactic violations in Spanish: An event-related potentials study

Language and Cognitive Processes, 2003

Event-related potentials (ERPs) were employed to compare word category and verb inflection violat... more Event-related potentials (ERPs) were employed to compare word category and verb inflection violations in Spanish. A similar frontal negativity was found between 250-400 ms for both violation types, suggesting that they equally disrupt initial syntactic analyses. Also, word category violations elicited a negativity at posterior electrodes larger than verb inflection anomalies and correct sentences within this time window, probably reflecting difficulties to semantically analyse phrase structure violations. Finally, a centroparietal positivity in the 500-700 ms interval was found for both error types. Both violations did not differ along the first half of this interval (500-600 ms), but larger effects for verb inflection violations were reported along Requests for reprints should be addressed to José A Hinojosa, Brain Mapping Unit,

Research paper thumbnail of The recognition potential during sentence presentation: stimulus probability, background stimuli, and SOA

International Journal of Psychophysiology, 2004

Recognition potential (RP) is an electrical brain response that has proved its usefulness for stu... more Recognition potential (RP) is an electrical brain response that has proved its usefulness for studying semantic processing of isolated words, and appears when subjects view meaningful stimuli embedded in a stream of background images at a high rate of presentation: the rapid stream stimulation paradigm (RSS). The present technical study is aimed at testing the validity of this procedure in the study of words within sentences. For this purpose, we varied word and background probability of appearance, the number of background stimuli preceding each word, and stimulus onset asynchrony. Probability did not have significant effects on RP, but it was found that a minimum number of two background stimuli preceding each word and a high rate (250 ms) of presentation are preferable for enhancing RP amplitude. The RSS paradigm would therefore improve the visibility-and, hence, refine the analysis-of a component that can nevertheless be obtained with more standard paradigms, such as rapid serial visual presentation, devoid of interspersed background stimuli.

Research paper thumbnail of The recognition potential and repetition effects

International Journal of Psychophysiology, 2002

The recognition potential RP is an electrical brain response peaking at 250 ms that appears when ... more The recognition potential RP is an electrical brain response peaking at 250 ms that appears when subjects view meaningful stimuli. Previous RP research was conducted in experimental conditions in which repetition effects could not be totally ruled out as influencing the generation of the RP response. The present study aims to elucidate whether repetition effects affect the topography and waveform of this component. For this purpose semantically correct, orthographically correct, strings of random letters, control and background stimuli were presented to 20 subjects following the rapid stream stimulation procedure and without repetition of any test stimulus. As previously, the RP showed its maximal amplitude at the PO7 electrode. It showed sensitivity to all levels of lexical processing, its response being maximal for semantically correct stimuli, and its topographical distribution was similar for all types of stimulus. Direct statistical comparisons with the data of a previous study where repetition effects could not be disregarded were performed, confirming the similarity between the results obtained in both experiments. The neural generators of the RP were placed again, as in previous studies, within the lingual gyrus. Although repetition effects have been reported to affect other semantic-related components such as the N400, they do not seem to affect either the topography or the waveform of the RP. ᮊ

Research paper thumbnail of The recognition potential in the study of formal thought disorder and abnormal semantic processing in schizophrenia

Schizophrenia Research, 2003

Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) i... more Abnormal activation of semantic networks may be the underlying basis for thought disorder (ThD) in patients with schizophrenia. However, whether this abnormality consists of increased or decreased activation is unclear. Previous behavioral and electrophysiological (N400) data have failed to yield consistent evidence for clarifying this hypothesis. One of the eventrelated potentials (ERP) components (the recognition potential, RP), presumably reflecting activation of specific semantic networks involved in ThD, has not been used to studies of schizophrenia, and may add additional information to support or refute this hypothesis. In an initial experiment, RP amplitude was reduced in schizophrenic patients, but particularly in those with ThD. In a second experiment, in addition to reduced overall RP amplitude, concrete words were shown to have higher amplitudes than abstract words in both patients and controls, supporting a relative integrity of the lexicon in ThD patients. RP reduction suggests that a fewer number of networks' elements are activated when an incoming word is processed, thus supporting hypoactivation of the semantic networks as the basis for ThD. D Abstract Concrete Abstract Concrete Abstract Alarms