Temporal characteristics of neural activity related to target detection during visual search (original) (raw)
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Information flow related to visual search assessed using magnetoencephalography
Brain research. Cognitive brain research, 2003
The sequence of neural activation during a visual search task was investigated using magnetoencephalography and the source locations for the activations were analyzed using a single-dipole algorithm. Five components (M1-5) were detected at mean latencies of 110, 146, 196, 250 and 333 ms in both of two different stimulus conditions; a target popped out in one stimulus condition (pop-out), while it did not in the other condition (non-pop-out). Statistical analysis showed that the M3 amplitude was larger and the M5 latency was shorter in the pop-out condition than in the non-pop-out condition, while there was no difference in the other components between the conditions. Neural sources were localized in the calcarine sulcus (M1) and the posterior fusiform gyrus (M2) of the hemisphere contralateral to the stimuli, the intraparietal sulcus and the posterior superior temporal sulcus (M3) in either of the hemispheres, and the calcarine sulcus (M4) of the same hemisphere in which the early p...
Nelson MJ, Murthy A, Schall JD. Neural control of visual search by frontal eye field: chronometry of neural events and race model processes..—We investigated the chronometry of neural processes in frontal eye fields of macaques performing double-step saccade visual search in which a conspicuous target changes location in the array on a random fraction of trials. Durations of computational processes producing a saccade to original and final target locations (GO1 and GO2, respectively) are derived from response times (RT) on different types of trials. In these data, GO2 tended to be faster than GO1, demonstrating that inhibition of the initial saccade did not delay production of the compensated saccade. Here, we measured the dynamics of visual, visuomovement, and movement neuron activity in relation to these processes by examining trials when neurons instantiated either process. First, we verified that saccades were initiated when the discharge rate of movement neurons reached a threshold that was invariant across RT and trial type. Second, the time when visual and visuomovement neurons selected the target and when movement neuron activity began to accumulate were not significantly different across trial type. Third, the interval from the beginning of accumulation to threshold of movement-related activity was significantly shorter when instantiating the GO2 relative to the GO1 process. Differences observed between monkeys are discussed. Fourth, random variation of RT was accounted for to some extent by random variation in both the onset and duration of selective activity of each neuron type but mostly by variation of movement neuron accumulation duration. These findings offer new insights into the sources of control of target selection and saccade production in dynamic environments. diffusion model; linking hypothesis; linking proposition; perceptual decision; decision making WHEN WE ARE PRESENTED WITH a typical cluttered visual scene, the production of a gaze shift to the location of a target item entails neural and supervenient psychological processes. According to one theoretical framework, these processes are comprised of distinct computational stages accomplishing the dissociable subtasks needed to select the target and
Cortical image density determines the probability of target discovery during active search
Vision Research, 2000
An analysis of target detection as a function of target eccentricity was made on eye movement data collected from three monkey subjects during active visual search. Target detection probability was invariant across array set size and eccentricity conditions when the cortical density of rele6ant stimuli surrounding the target was held constant. When target color was used to guide search, the effective cortical density was the density of stimuli that shared the target's color. Thus the passive constraint of cortical magnification in combination with an active selection for a stimulus attribute, in this case color, sets the spatial framework for detection of the target.
2010
Numerous studies have described different functional cell types in the frontal eye field (FEF), but the reliability of the distinction between these types has been uncertain. Studies in other brain areas have described specific differences in the width of action potentials recorded from different cell types. To substantiate the functionally defined cell types encountered in FEF, we measured the width of spikes of visual, movement, and visuomovement types of FEF neurons in macaque monkeys. We show that visuomovement neurons had the thinnest spikes, consistent with a role in local processing. Movement neurons had the widest spikes, consistent with their role in sending eye movement commands to subcortical structures such as the superior colliculus. Visual neurons had wider spikes than visuomovement neurons, consistent with their role in receiving projections from occipital and parietal cortex. These results show how structure and function of FEF can be linked to guide inferences about neuronal architecture. Local circuit neurons immunoreactive for calretinin, calbindin D-28k or parvalbumin in monkey prefrontal cortex: distribution and morphology. J Comp Neurol 341: 95-116, 1994. Connors BW, Gutnick MJ. Intrinsic firing patterns of diverse neocortical neurons. Trends Neurosci 13: 99 -104, 1990. Constantinidis C, Goldman-Rakic PS. Correlated discharges among putative pyramidal neurons and interneurons in the primate prefrontal cortex. J Neurophysiol 88: 3487-3497, 2002. Csicsvari J, Hirase H, Czurkó A, Mamiya A, Buzsáki G. Oscillatory coupling of hippocampal pyramidal cells and interneurons in the behaving rat. J Neurosci 19: 274 -287, 1999. DiCarlo JJ, Maunsell JH. Using neuronal latency to determine sensory-motor processing pathways in reaction time tasks. J Neurophysiol 93: 2974 -2986, 2005. Dow BM. Functional classes of cells and their laminar distribution in monkey visual cortex. J Neurophysiol 37: 927-946, 1974. Fries W. Cortical projections to the superior colliculus in the macaque monkey: a retrograde study using horseradish peroxidase. J Comp Neurol 230: 55-76, 1984. Goldberg ME, Bushnell MC. Behavioral enhancement of visual responses in monkey cerebral cortex. II. Modulation in frontal eye fields specifically related to saccades. J Neurophysiol 46: 773-787, 1981. González-Burgos G, Krimer LS, Povysheva NV, Barrionuevo G, Lewis DA. Functional properties of fast spiking interneurons and their synaptic connections with pyramidal cells in primate dorsolateral prefrontal cortex. J Neurophysiol 93: 942-953, 2005. Gur M, Beylin A, Snodderly DM. Physiological properties of macaque V1
NeuroImage, 2007
Both animal and human studies suggest that the efficiency with which we are able to grasp objects is attributable to a repertoire of motor signals derived directly from vision. This is in general agreement with the long-held belief that the automatic generation of motor signals by the perception of objects is based on the actions they afford. In this study, we used magnetoencephalography (MEG) to determine the spatial distribution and temporal dynamics of brain regions activated during passive viewing of object and non-object targets that varied in the extent to which they afforded a grasping action. Synthetic Aperture Magnetometry (SAM) was used to localize task-related oscillatory power changes within specific frequency bands, and the time course of activity within given regions-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. Both single subject and group-averaged data on the spatial distribution of brain activity are presented. We show that: (i) significant reductions in 10-25 Hz activity within extrastriate cortex, occipito-temporal cortex, sensori-motor cortex and cerebellum were evident with passive viewing of both objects and non-objects; and (ii) reductions in oscillatory activity within the posterior part of the superior parietal cortex (area Ba7) were only evident with the perception of objects. Assuming that focal reductions in low-frequency oscillations (< 30 Hz) reflect areas of heightened neural activity, we conclude that: (i) activity within a network of brain areas, including the sensori-motor cortex, is not critically dependent on stimulus type and may reflect general changes in visual attention; and (ii) the posterior part of the superior parietal cortex, area Ba7, is activated preferentially by objects and may play a role in computations related to grasping.
Distinct neural substrates for visual search amongst spatial versus temporal distractors
Brain research. Cognitive brain research, 2003
Whether the contribution of the superior parietal cortex (BA7) to attention-demanding tasks is strictly spatial in nature remains unresolved. We used functional magnetic resonance imaging to explore the behavioural and neuroanatomical correlates of non-spatial search for a conjunction of features within a stream of temporally-distracting stimuli. In addition, we compared these data to those from a conventional visuo-spatial search task, performed by the same subjects, in order to determine the specificity of right BA7 activation. Mode of stimulus-distribution (spatial versus temporal) and search type (target defined by a single feature or a conjunction of features) were manipulated in a 2 x 2 factorial design. Behaviourally, the temporal conjunction task was shown to index temporal selective attention. Accuracy of detecting a second target varied with the temporal proximity of two successive targets when subjects searched for a conjunction of features, but not a single feature. The ...
The roles of cortical image separation and size in active visual search performance
Journal of Vision, 2007
Our previous research examined the effects of target eccentricity and global stimulus density on target detection during active visual search in monkey. Here, eye movement data collected from three human subjects on a standard single-color Ts and Ls task with varying set sizes were used to analyze the probability of target detection as a function of local stimulus density. Search performance was found to exhibit a systematic dependence on local stimulus density around the target and as a function of target eccentricity when density is calculated with respect to cortical space, in accordance with a model of the retinocortical geometrical transformation of image data onto the surface of V1. Density as measured by nearest neighbor separation and target image size as calculated from target eccentricity were found to contribute independently to search performance when measured with respect to cortical space but not with standard visual space. Density relationships to performance did not differ when target and nearest neighbor were on opposite sides of the vertical meridian, underscoring the hypothesis that such interactions were occurring within higher visual areas. The cortical separation of items appears to be the major determinant of array set size effects in active visual search.
NeuroReport, 2008
The frontal eye ¢elds (FEFs) and posterior parietal cortex (PPC) are important for target detection in conjunction visual search but the relative timings of their contribution have not been compared directly. We addressed this using temporally speci¢c double pulse transcranial magnetic stimulation delivered at di¡erent times over FEFs and PPC during performance of a visual search task. Disruption of performance was earlier (0/40 ms) with FEF stimulation than with PPC stimulation (120/160 ms), revealing a clear and substantial temporal dissociation of the involvement of these two areas in conjunction visual search. We discuss these timings with reference to the respective roles of FEF and PPC in the modulation of extrastriate visual areas and selection of responses. NeuroReport 00:000^000
Cue-Invariant Activation in Object-Related Areas of the Human Occipital Lobe
Neuron, 1998
† Diagnostic Imaging Department channels DeYoe et al., 1994) and for convergence of several primary cues even The Chaim Sheba Medical Center Tel Hashomer 52621 at the level of single cortical neurons . Similarly, studies of anatomical connections indicate Israel ‡ School of Cognitive and Computing Sciences the existence of parallel specialized cortical streams but also show substantial interstream University of Sussex, Falmer Brighton BN1 9QH communication both between areas (reviewed by and in the intrinsic neuronal United Kingdom architecture . Several neuroimaging studies have attempted to address the issue of convergence of cues in the human Summary visual cortex. On the one hand, evidence for convergence of visual cues in specific areas was provided both The extent to which primary visual cues such as moby , who demonstrated that human tion or luminance are segregated in different cortical motion area V5/MT can be activated by motion-fromareas is a subject of controversy. To address this ishue, and by , who showed that kisue, we examined cortical activation in the human netic-and luminance-defined gratings activate a speoccipital lobe using functional magnetic resonance cific human cortical region, Kinetic Occipital (KO). On imaging (fMRI) while subjects performed a fixed visual the other hand, Gulyas et al. (1994) showed that formtask, object recognition, using three different primary from-color stimuli activate a different anatomical region visual cues: motion, texture, or luminance contrast. In than form-from-motion, suggesting segregation of some the first experiment, a region located on the lateral visual cues.