Masatoshi Yoshida | National Institute for Physiological Sciences (NIPS) (original) (raw)

Papers by Masatoshi Yoshida

Neuroscience Research, Jan 1, 2009

Neuroscience Research, Jan 1, 2007

Superior colliculus (SC) is supposed to be a critical region for visuomotor transformation relate... more Superior colliculus (SC) is supposed to be a critical region for visuomotor transformation related to saccade execution and many SC neurons exhibit visual and/or saccade-related activities. Monkeys with damage to the primary visual cortex (V1) can make saccades to visual stimuli in their affected visual field. To examine the neuronal basis for this residual ability, we recorded neuronal activities in SC of the monkey with unilateral V1 lesion during visually guided saccades. In the ipsilesional SC we found visual responses to the target in their response field, while their peak firing rate decreased and their onset and peak latencies were delayed, compared with those of contralesional SC. Our results show that ipsilesional SC can be driven by visual stimuli and would be involved in visual-oculomotor processing, but somewhat in a different manner from the intact hemifield.

Neuroscience Research, Jan 1, 2009

Journal of Vision, Jan 1, 2008

Abstract Human blindsight patients, who have damages in the primary visual cortex (V1), can discr... more Abstract Human blindsight patients, who have damages in the primary visual cortex (V1), can discriminate the target positions while they deny awareness of the targets. Macaque monkeys with a unilateral lesion in V1 have been used as an animal model of blindsight. ...

Neuroscience …, Jan 1, 2009

We investigated the spatial distribution of simple-spike response types of Purkinje cells (P-cell... more We investigated the spatial distribution of simple-spike response types of Purkinje cells (P-cells) within the cerebellar nodulus and uvula during sinusoidal head rotation in vertical plane in awake cats. Cells demonstrating the strongest response to the roll plane tended to be located in a parasagittal band extending more than 1.0 mm lateral to the midline, while those with the strongest response to pitch plane tended to be located in a band extending up to 1.0 mm from the midline. These findings suggest that there are at least 2 sagittal functional zones with a rostrocaudal extent in the search area examined in the present study. Such spatial information might be transmitted to the brainstem nuclei to control motor dynamics for the optokinetic responses under head-tilt conditions in each specific plane.

Journal of Vision, Jan 1, 2007

Abstract Some of the patients with damages in the primary visual cortex (V1) retain their ability... more Abstract Some of the patients with damages in the primary visual cortex (V1) retain their ability to localize visual targets in their affected hemifield ('blindsight'or 'residual vision'). One of the controversies about blindsight is whether it is a form of near-threshold vision or ...

Neuroscience Research, Jan 1, 2010

The Journal of Neuroscience, Jan 1, 2011

In the primate brain, the primary visual cortex (V1) is a major source of visual information proc... more In the primate brain, the primary visual cortex (V1) is a major source of visual information processing in the cerebral cortex, although some patients and monkeys with damage to the V1 show visually guided behaviors in the visual field affected by the damage. Until now, behaviors of the surviving brain regions after damage to V1 and their contribution to the residual visual functions remain unclear. Here, we report that the monkeys with a unilateral lesion of V1 can make not only visually guided saccades but also memory-guided saccades (MGS) into the affected visual field. Furthermore, while the monkeys were performing the MGS task, sustained activity was observed in a large fraction of the neurons in the superior colliculus ipsilateral to the lesion, which has been supposed as a key node for recovery after damage to V1. These neurons maintained the spatial information throughout the delay period regardless of whether they exhibited saccadic bursts or not, which was not the case on the intact side. Error analysis revealed that the sustained activity was correlated with monkeys' behavioral outcome. These results suggest that the ipsilesional SC might function as a neural substrate for spatial memory in the affected visual field. Our findings provide new insight into the understanding of the compensatory mechanisms after damage to V1.

Journal of Cognitive Neuroscience, Jan 1, 2011

Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of or... more Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of orienting to an ensuing target at the same location. Recent studies revealed that the superior colliculus (SC) is involved in these facilitatory and inhibitory cueing effects on saccade; however, as the SC receives inputs both directly from the retina (retino-tectal pathway) and indirectly from visual cortices (geniculostriate pathway), it is unclear which visual pathway contributes to the effects. We investigated this issue using monkeys with lesions in the primary visual cortex (V1), thus depriving the SC of the geniculostriate pathway and leaving the retino-tectal pathway intact. We found that the inhibitory cueing effect was selectively impaired and the facilitatory cueing effect was spared after V1 lesions. The results suggest that the geniculostriate and the retino-tectal pathways are differentially involved in the generation of cueing effects on saccade: The former is critically involved in the inhibitory effect whereas the latter alone can induce the facilitatory effect. The results provide the first direct evidence for the involvement of the geniculostriate pathway in the inhibitory cueing effect and further imply that the more recent evolution of the geniculostriate pathway in higher mammals improves the efficiency of visual search by inhibiting orienting to a previously attended location.

Current opinion in neurobiology, Jan 1, 2009

A number of previous articles on blindsight have stressed that even after the lesion of the prima... more A number of previous articles on blindsight have stressed that even after the lesion of the primary visual cortex (V1), subjects can perform visually guided saccades toward the targets in the blind field and that the extrageniculate visual pathway which bypasses the V1 can control the saccades by itself. However, in monkey model of V1 lesion, about two months of time is needed for recovery, suggesting that the extrageniculate visual pathway cannot immediately take over the function of the geniculo-striatal pathway, and on close look at the dynamics of saccades, saccades became ballistic and online corrections of trajectories and velocities were impaired, and that decision threshold for saccade initiation was lowered. On the basis of these findings, we propose that the visual signal through V1 is necessary for deliberate control of saccades.

Comptes Rendus de l' …, Jan 1, 1998

The Journal of …, Jan 1, 2008

Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual sti... more Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual stimuli in their contralateral ("affected") hemifield, but their sensitivity to luminance contrast is reduced. We examined whether the effects of V1 lesions were restricted to vision or included later stages of visual-oculomotor processing. Monkeys with unilateral V1 lesions were tested with a visually guided saccade task with stimuli in various spatial positions and of various luminance contrasts. Saccades to the stimuli in the affected hemifield were compared with those to the near-threshold stimuli in the normal hemifield so that the performances of localization were similar. Scatter in the end points of saccades to the affected hemifield was much larger than that of saccades to the near-threshold stimuli in the normal hemifield. Additional analysis revealed that this was because the initial directional error was not as sufficiently compensated as it was in the normal hemifield. The distribution of saccadic reaction times in the affected hemifield tended to be narrow. We modeled the distribution of saccadic reaction times by a modified diffusion model and obtained evidence that the decision threshold for initiation of saccades to the affected hemifield was lower than that for saccades to the normal hemifield. These results suggest that the geniculostriate pathway is crucial for on-line compensatory mechanisms of saccadic control and for decision processes. We propose that these results reflect deficits in deliberate control of visual-oculomotor processing after V1 lesions, which may parallel loss of visual awareness in human blindsight patients.

European Journal …, Jan 1, 2003

The macaque inferotemporal cortex, which is involved in encoding and retrieval of visual long-ter... more The macaque inferotemporal cortex, which is involved in encoding and retrieval of visual long-term memory, consists of two distinct but mutually interconnected areas: area TE (TE) and area 36 (A36). In the present study, we compared delay-period activities of the two subdivisions in terms of their signal contents. We recorded single-unit activities from TE and A36 during a delayed pair association task, in which monkeys were required to choose the paired associate of a cue stimulus after a delay period. The stimulus-selective delay-period activities of single neurons were characterized by using partial correlation coefficients of delay-period activities for each cue stimulus with the cue-period responses to that stimulus (cue-holding index, CHI) and with the cue-period responses to its paired associate (pair-recall index, PRI). The delay-period activities of TE neurons preferentially represented the paired associate (PRI, median = 0.54) rather than the cue stimulus itself (CHI, 0.23) (P < 0.001, n = 70), while the delay-period activities of A36 neurons retained both the cue stimulus and its paired associate equivalently (CHI, 0.44; PRI, 0.46) (P = 0.78, n = 38). These results indicate that the signal contents of delay-period activities differ between the two subdivisions: TE mostly represents a sought target that is retrieved from long-term memory, while A36 in addition retains cue-stimulus that is transmitted from earlier visual areas.

Proceedings of the …, Jan 1, 2003

A number of studies have shown that the perirhinal (PRh) cortex, which is part of the medial temp... more A number of studies have shown that the perirhinal (PRh) cortex, which is part of the medial temporal lobe memory system, plays an important role in declarative long-term memory. The PRh cortex contains neurons that represent visual long-term memory. The aim of the present study is to characterize the anatomical organization of forward projections that mediate information flow from visual area TE to memory neurons in the PRh cortex. In monkeys performing a visual pair-association memory task, we conducted an extensive mapping of neuronal responses in the anteroventral part of area TE (TEav) and area 36 (A36) of the PRh cortex. Then, three retrograde tracers were separately injected into A36 and the distribution of retrograde labels in TEav was analyzed. We focused on the degree of divergent projections from TEav to memory neurons in A36, because the highly divergent nature of these forward fiber projections has been implicated in memory function. We found that the degree of divergent projection to memory neurons in A36 was smaller from the TEav neurons selective to learned pictures than from the nonselective TEav neurons. This result demonstrates that the anatomical difference (the divergence) correlates with the physiological difference (selectivity of TEav neurons to the learned pictures). Because the physiological difference is attributed to whether the projections are involved in information transmission required for memory neurons in A36, it can be speculated that the reduced divergent projection resulted from acquisition of visual long-term memory, possibly through retraction of the projecting axon collaterals.

The Journal of neuroscience, Jan 1, 2003

The macaque inferotemporal (IT) cortex, which serves as the storehouse of visual long-term memory... more The macaque inferotemporal (IT) cortex, which serves as the storehouse of visual long-term memory, consists of two distinct but mutually interconnected areas: area TE (TE) and area 36 (A36). In the present study, we tested whether memory encoding is put forward at this stage, i.e., whether association between the representations of different but semantically linked objects proceeds forward from TE to A36. To address this question, we trained monkeys in a pair-association (PA) memory task, after which single-unit activities were recorded from TE and A36 during PA trials. Neurons in both areas showed stimulus-selective cue responses (347 in TE, 76 in A36; "cue-selective neurons") that provided, at the population level, mnemonic linkage between the paired associates. The percentage of neurons in which responses to the paired associates were significantly (p Ͻ 0.01) correlated at the single-neuron level ("pair-coding neuron") dramatically increased from TE (4.9% of the cue-selective neurons) to A36 (33%). The pair-coding neurons in A36 were further separable into Type1 (68%) and Type2 (32%) on the basis of their initial transient responses after cue stimulus presentation. Type1 neurons, but not Type2 neurons, began to encode association between paired stimuli as soon as they exhibited stimulus selectivity. Thus, the representation of long-term memory encoded by Type1 neurons in A36 is likely substantiated without feedback input from other higher centers. Therefore, we conclude that association between the representations of the paired associates proceeds forward at this critical step within IT cortex, suggesting selective convergence onto a single A36 neuron from two TE neurons that encode separate visual objects.

Neuroscience Research, Jan 1, 2009

Neuroscience Research, Jan 1, 2007

Superior colliculus (SC) is supposed to be a critical region for visuomotor transformation relate... more Superior colliculus (SC) is supposed to be a critical region for visuomotor transformation related to saccade execution and many SC neurons exhibit visual and/or saccade-related activities. Monkeys with damage to the primary visual cortex (V1) can make saccades to visual stimuli in their affected visual field. To examine the neuronal basis for this residual ability, we recorded neuronal activities in SC of the monkey with unilateral V1 lesion during visually guided saccades. In the ipsilesional SC we found visual responses to the target in their response field, while their peak firing rate decreased and their onset and peak latencies were delayed, compared with those of contralesional SC. Our results show that ipsilesional SC can be driven by visual stimuli and would be involved in visual-oculomotor processing, but somewhat in a different manner from the intact hemifield.

Neuroscience Research, Jan 1, 2009

Journal of Vision, Jan 1, 2008

Abstract Human blindsight patients, who have damages in the primary visual cortex (V1), can discr... more Abstract Human blindsight patients, who have damages in the primary visual cortex (V1), can discriminate the target positions while they deny awareness of the targets. Macaque monkeys with a unilateral lesion in V1 have been used as an animal model of blindsight. ...

Neuroscience …, Jan 1, 2009

We investigated the spatial distribution of simple-spike response types of Purkinje cells (P-cell... more We investigated the spatial distribution of simple-spike response types of Purkinje cells (P-cells) within the cerebellar nodulus and uvula during sinusoidal head rotation in vertical plane in awake cats. Cells demonstrating the strongest response to the roll plane tended to be located in a parasagittal band extending more than 1.0 mm lateral to the midline, while those with the strongest response to pitch plane tended to be located in a band extending up to 1.0 mm from the midline. These findings suggest that there are at least 2 sagittal functional zones with a rostrocaudal extent in the search area examined in the present study. Such spatial information might be transmitted to the brainstem nuclei to control motor dynamics for the optokinetic responses under head-tilt conditions in each specific plane.

Journal of Vision, Jan 1, 2007

Abstract Some of the patients with damages in the primary visual cortex (V1) retain their ability... more Abstract Some of the patients with damages in the primary visual cortex (V1) retain their ability to localize visual targets in their affected hemifield ('blindsight'or 'residual vision'). One of the controversies about blindsight is whether it is a form of near-threshold vision or ...

Neuroscience Research, Jan 1, 2010

The Journal of Neuroscience, Jan 1, 2011

In the primate brain, the primary visual cortex (V1) is a major source of visual information proc... more In the primate brain, the primary visual cortex (V1) is a major source of visual information processing in the cerebral cortex, although some patients and monkeys with damage to the V1 show visually guided behaviors in the visual field affected by the damage. Until now, behaviors of the surviving brain regions after damage to V1 and their contribution to the residual visual functions remain unclear. Here, we report that the monkeys with a unilateral lesion of V1 can make not only visually guided saccades but also memory-guided saccades (MGS) into the affected visual field. Furthermore, while the monkeys were performing the MGS task, sustained activity was observed in a large fraction of the neurons in the superior colliculus ipsilateral to the lesion, which has been supposed as a key node for recovery after damage to V1. These neurons maintained the spatial information throughout the delay period regardless of whether they exhibited saccadic bursts or not, which was not the case on the intact side. Error analysis revealed that the sustained activity was correlated with monkeys' behavioral outcome. These results suggest that the ipsilesional SC might function as a neural substrate for spatial memory in the affected visual field. Our findings provide new insight into the understanding of the compensatory mechanisms after damage to V1.

Journal of Cognitive Neuroscience, Jan 1, 2011

Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of or... more Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of orienting to an ensuing target at the same location. Recent studies revealed that the superior colliculus (SC) is involved in these facilitatory and inhibitory cueing effects on saccade; however, as the SC receives inputs both directly from the retina (retino-tectal pathway) and indirectly from visual cortices (geniculostriate pathway), it is unclear which visual pathway contributes to the effects. We investigated this issue using monkeys with lesions in the primary visual cortex (V1), thus depriving the SC of the geniculostriate pathway and leaving the retino-tectal pathway intact. We found that the inhibitory cueing effect was selectively impaired and the facilitatory cueing effect was spared after V1 lesions. The results suggest that the geniculostriate and the retino-tectal pathways are differentially involved in the generation of cueing effects on saccade: The former is critically involved in the inhibitory effect whereas the latter alone can induce the facilitatory effect. The results provide the first direct evidence for the involvement of the geniculostriate pathway in the inhibitory cueing effect and further imply that the more recent evolution of the geniculostriate pathway in higher mammals improves the efficiency of visual search by inhibiting orienting to a previously attended location.

Current opinion in neurobiology, Jan 1, 2009

A number of previous articles on blindsight have stressed that even after the lesion of the prima... more A number of previous articles on blindsight have stressed that even after the lesion of the primary visual cortex (V1), subjects can perform visually guided saccades toward the targets in the blind field and that the extrageniculate visual pathway which bypasses the V1 can control the saccades by itself. However, in monkey model of V1 lesion, about two months of time is needed for recovery, suggesting that the extrageniculate visual pathway cannot immediately take over the function of the geniculo-striatal pathway, and on close look at the dynamics of saccades, saccades became ballistic and online corrections of trajectories and velocities were impaired, and that decision threshold for saccade initiation was lowered. On the basis of these findings, we propose that the visual signal through V1 is necessary for deliberate control of saccades.

Comptes Rendus de l' …, Jan 1, 1998

The Journal of …, Jan 1, 2008

Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual sti... more Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual stimuli in their contralateral ("affected") hemifield, but their sensitivity to luminance contrast is reduced. We examined whether the effects of V1 lesions were restricted to vision or included later stages of visual-oculomotor processing. Monkeys with unilateral V1 lesions were tested with a visually guided saccade task with stimuli in various spatial positions and of various luminance contrasts. Saccades to the stimuli in the affected hemifield were compared with those to the near-threshold stimuli in the normal hemifield so that the performances of localization were similar. Scatter in the end points of saccades to the affected hemifield was much larger than that of saccades to the near-threshold stimuli in the normal hemifield. Additional analysis revealed that this was because the initial directional error was not as sufficiently compensated as it was in the normal hemifield. The distribution of saccadic reaction times in the affected hemifield tended to be narrow. We modeled the distribution of saccadic reaction times by a modified diffusion model and obtained evidence that the decision threshold for initiation of saccades to the affected hemifield was lower than that for saccades to the normal hemifield. These results suggest that the geniculostriate pathway is crucial for on-line compensatory mechanisms of saccadic control and for decision processes. We propose that these results reflect deficits in deliberate control of visual-oculomotor processing after V1 lesions, which may parallel loss of visual awareness in human blindsight patients.

European Journal …, Jan 1, 2003

The macaque inferotemporal cortex, which is involved in encoding and retrieval of visual long-ter... more The macaque inferotemporal cortex, which is involved in encoding and retrieval of visual long-term memory, consists of two distinct but mutually interconnected areas: area TE (TE) and area 36 (A36). In the present study, we compared delay-period activities of the two subdivisions in terms of their signal contents. We recorded single-unit activities from TE and A36 during a delayed pair association task, in which monkeys were required to choose the paired associate of a cue stimulus after a delay period. The stimulus-selective delay-period activities of single neurons were characterized by using partial correlation coefficients of delay-period activities for each cue stimulus with the cue-period responses to that stimulus (cue-holding index, CHI) and with the cue-period responses to its paired associate (pair-recall index, PRI). The delay-period activities of TE neurons preferentially represented the paired associate (PRI, median = 0.54) rather than the cue stimulus itself (CHI, 0.23) (P < 0.001, n = 70), while the delay-period activities of A36 neurons retained both the cue stimulus and its paired associate equivalently (CHI, 0.44; PRI, 0.46) (P = 0.78, n = 38). These results indicate that the signal contents of delay-period activities differ between the two subdivisions: TE mostly represents a sought target that is retrieved from long-term memory, while A36 in addition retains cue-stimulus that is transmitted from earlier visual areas.

Proceedings of the …, Jan 1, 2003

A number of studies have shown that the perirhinal (PRh) cortex, which is part of the medial temp... more A number of studies have shown that the perirhinal (PRh) cortex, which is part of the medial temporal lobe memory system, plays an important role in declarative long-term memory. The PRh cortex contains neurons that represent visual long-term memory. The aim of the present study is to characterize the anatomical organization of forward projections that mediate information flow from visual area TE to memory neurons in the PRh cortex. In monkeys performing a visual pair-association memory task, we conducted an extensive mapping of neuronal responses in the anteroventral part of area TE (TEav) and area 36 (A36) of the PRh cortex. Then, three retrograde tracers were separately injected into A36 and the distribution of retrograde labels in TEav was analyzed. We focused on the degree of divergent projections from TEav to memory neurons in A36, because the highly divergent nature of these forward fiber projections has been implicated in memory function. We found that the degree of divergent projection to memory neurons in A36 was smaller from the TEav neurons selective to learned pictures than from the nonselective TEav neurons. This result demonstrates that the anatomical difference (the divergence) correlates with the physiological difference (selectivity of TEav neurons to the learned pictures). Because the physiological difference is attributed to whether the projections are involved in information transmission required for memory neurons in A36, it can be speculated that the reduced divergent projection resulted from acquisition of visual long-term memory, possibly through retraction of the projecting axon collaterals.

The Journal of neuroscience, Jan 1, 2003

The macaque inferotemporal (IT) cortex, which serves as the storehouse of visual long-term memory... more The macaque inferotemporal (IT) cortex, which serves as the storehouse of visual long-term memory, consists of two distinct but mutually interconnected areas: area TE (TE) and area 36 (A36). In the present study, we tested whether memory encoding is put forward at this stage, i.e., whether association between the representations of different but semantically linked objects proceeds forward from TE to A36. To address this question, we trained monkeys in a pair-association (PA) memory task, after which single-unit activities were recorded from TE and A36 during PA trials. Neurons in both areas showed stimulus-selective cue responses (347 in TE, 76 in A36; "cue-selective neurons") that provided, at the population level, mnemonic linkage between the paired associates. The percentage of neurons in which responses to the paired associates were significantly (p Ͻ 0.01) correlated at the single-neuron level ("pair-coding neuron") dramatically increased from TE (4.9% of the cue-selective neurons) to A36 (33%). The pair-coding neurons in A36 were further separable into Type1 (68%) and Type2 (32%) on the basis of their initial transient responses after cue stimulus presentation. Type1 neurons, but not Type2 neurons, began to encode association between paired stimuli as soon as they exhibited stimulus selectivity. Thus, the representation of long-term memory encoded by Type1 neurons in A36 is likely substantiated without feedback input from other higher centers. Therefore, we conclude that association between the representations of the paired associates proceeds forward at this critical step within IT cortex, suggesting selective convergence onto a single A36 neuron from two TE neurons that encode separate visual objects.