Neurons In Inferior Temporal Cortex Research Articles

Putative excitatory and inhibitory neurons in the macaque inferior temporal cortex play distinct roles in core object recognition

Putative excitatory and inhibitory neurons in the macaque inferior temporal cortex play distinct roles in core object recognition

Temporal continuity shapes visual responses of macaque face patch neurons

Macaque inferior temporal cortex neurons respond selectively to complex visual images, with recent work showing that they are also entrained reliably by the evolving content of natural movies. To what extent does temporal continuity itself shape the responses of high-level visual neurons? We addressed this question by measuring how cells in face-selective regions of the macaque visual cortex were affected by the manipulation of a movie's temporal structure. Sampling a 5-min movie at 1s intervals, we measured neural responses to randomized, brief stimuli of different lengths, ranging from 800ms dynamic movie snippets to 100ms static frames. We found that the disruption of temporal continuity strongly altered neural response profiles, particularly in the early response period after stimulus onset. The results suggest that models of visual system function based on discrete and randomized visual presentations may not translate well to the brain's natural modes of operation.

Neurons in inferior temporal cortex are sensitive to motion trajectory during degraded object recognition.

Our brains continuously acquire sensory information and make judgments even when visual information is limited. In some circumstances, an ambiguous object can be recognized from how it moves, such as an animal hopping or a plane flying overhead. Yet it remains unclear how movement is processed by brain areas involved in visual object recognition. Here we investigate whether inferior temporal (IT) cortex, an area known for its relevance in visual form processing, has access to motion information during recognition. We developed a matching task that required monkeys to recognize moving shapes with variable levels of shape degradation. Neural recordings in area IT showed that, surprisingly, some IT neurons responded stronger to degraded shapes than clear ones. Furthermore, neurons exhibited motion sensitivity at different times during the presentation of the blurry target. Population decoding analyses showed that motion patterns could be decoded from IT neuron pseudo-populations. Contrary to previous findings, these results suggest that neurons in IT can integrate visual motion and shape information, particularly when shape information is degraded, in a way that has been previously overlooked. Our results highlight the importance of using challenging multifeature recognition tasks to understand the role of area IT in naturalistic visual object recognition.

Encoding of Partially Occluded and Occluding Objects in Primate Inferior Temporal Cortex.

Object segmentation-the process of parsing visual scenes-is essential for object recognition and scene understanding. We investigated how responses of neurons in macaque inferior temporal (IT) cortex contribute to object segmentation under partial occlusion. Specifically, we asked whether IT responses to occluding and occluded objects are bound together as in the visual image or linearly separable reflecting their segmentation. We recorded the activity of 121 IT neurons while two male animals performed a shape discrimination task under partial occlusion. We found that for a majority (60%) of neurons, responses were enhanced by partial occlusion, but they were only weakly shape selective for the discriminanda at all levels of occlusion. Enhancement of IT responses in these neurons depended largely on the area of occlusion but only minimally on the color and shape of the occluding dots. In contrast to the above group of neurons, a sizable minority responded best to the unoccluded stimulus and showed strong selectivity for the shape of the discriminanda. In these neurons, response magnitude and shape selectivity declined with increasing levels of occlusion. Simulations revealed that the response characteristics of both classes of neurons were consistent with a model in which the responses to the occluded shape and the occluders are weighted separately and linearly combined. Overall, our results support the hypothesis that information about occluded and occluding stimuli are linearly separable and easily decodable from IT responses and that IT neurons encode a segmented representation of the visual scene.SIGNIFICANCE STATEMENT Recognizing partially occluded objects can be challenging, yet the primate visual system achieves it rapidly and effortlessly. For successful recognition in the face of occlusion, segmentation of the occluded and occluding objects is a critical first step. Using a combination of experimental data and simulations, here we demonstrate that responses of neurons in macaque IT cortex, the highest stage of the form processing pathway, reflect occluded and occluding stimuli as segmented components and are not bound together as they appear in the visual image. These results support the idea that segmentation and perception of occluded and occluding stimuli are directly mirrored in the responses of neurons in the highest form processing stages.

Comparison of neuronal responses in primate inferior-temporal cortex and feed-forward deep neural network model with regard to information processing of faces.

Feed-forward deep neural networks have better performance in object categorization tasks than other models of computer vision. To understand the relationship between feed-forward deep networks and the primate brain, we investigated representations of upright and inverted faces in a convolutional deep neural network model and compared them with representations by neurons in the monkey anterior inferior-temporal cortex, area TE. We applied principal component analysis to feature vectors in each model layer to visualize the relationship between the vectors of the upright and inverted faces. The vectors of the upright and inverted monkey faces were more separated through the convolution layers. In the fully-connected layers, the separation among human individuals for upright faces was larger than for inverted faces. The Spearman correlation between each model layer and TE neurons reached a maximum at the fully-connected layers. These results indicate that the processing of faces in the fully-connected layers might resemble the asymmetric representation of upright and inverted faces by the TE neurons. The separation of upright and inverted faces might take place by feed-forward processing in the visual cortex, and separations among human individuals for upright faces, which were larger than those for inverted faces, might occur in area TE.

Within- and between-hemifield generalization of repetition suppression in inferior temporal cortex.

The decrease in response with stimulus repetition is a common property observed in many sensory brain areas. This repetition suppression (RS) is ubiquitous in neurons of macaque inferior temporal (IT) cortex, the end-stage of the ventral visual pathway. The neural mechanisms of RS in IT are still unclear, and one possibility is that it is inherited from areas upstream to IT that show also RS. Since neurons in IT have larger receptive fields compared with earlier visual areas, we examined the inheritance hypothesis by presenting adapter and test stimuli at widely different spatial locations along both vertical and horizontal meridians and across hemifields. RS was present for distances between adapter and test stimuli up to 22° and when the two stimuli were presented in different hemifields. Also, we examined the position tolerance of the stimulus selectivity of adaptation by comparing the responses to a test stimulus following the same (repetition trial) or a different (alternation trial) adapter at a position different from the test stimulus. Stimulus-selective adaptation was still present and consistently stronger in the later phase of the response for distances up to 18°. Finally, we observed stimulus-selective adaptation in repetition trials even without a measurable excitatory response to the adapter stimulus. To accommodate these and previous data, we propose that at least part of the stimulus-selective adaptation in IT is based on short-term plasticity mechanisms within IT and/or reflects top-down activity from areas downstream to IT.NEW & NOTEWORTHY Neurons in inferior temporal cortex reduce their response when stimuli are repeated. To assess whether this repetition suppression is inherited from upstream visual areas, we examined the extent of its spatial generalization. We observed stimulus-selective adaptation when adapter and test stimuli were presented at widely different spatial positions and in different hemifields. These data suggest that at least part of the repetition suppression originates within inferior temporal cortex and/or reflects feedback from downstream areas.

Probing the Mechanisms of Repetition Suppression in Inferior Temporal Cortex with Optogenetics

Neurons in macaque inferior temporal (IT) cortex show a decrease in the response with stimulus repetition, known as repetition suppression (RS). Several mechanisms may contribute to RS in IT, such asfiring rate-dependent fatigue and transsynaptic mechanisms, like synaptic depression or reduced input from neurons within the same area or from up- or downstream areas. We examined the role of firing rate fatigue and transsynaptic mechanisms by stimulating directly IT neurons using optogenetics and measured the effect of photo-stimulation on their responses using timing parameters that resulted in RS for visual stimuli. Photo-stimulation of IT neurons resulted in a marginally decreased probability of spiking activity to a subsequent photo-stimulationor to a subsequent low-contrast visual stimulus. This response reduction was small relative to that for repeated visual stimuli and was related to post-stimulation inhibition of the activity during the interval between adapter and test stimuli. Presentation of a visual adapter did not change the response to subsequent photo-stimulation. In neurons whose response to the visual adapter was inhibited by simultaneous photo-stimulation, RS to visual stimuli was unaffected. Overall, these data imply that RS in IT has a transsynaptic origin, with little or no contribution of intrinsic firing rate fatigue. In addition, they suggest a limited contribution of both local synaptic depression and reduced input from nearby IT neurons, whose responses were postulated to be decreased by firing rate fatigue, to RS in IT.

Probing the mechanisms of adaptation of macaque inferotemporal neurons with optogenetics

Event Abstract Back to Event Probing the mechanisms of adaptation of macaque inferotemporal neurons with optogenetics Francesco Fabbrini1*, Chris Van Den Haute1, Marina De Vitis1, Veerle Baekelandt1, Wim Vanduffel1 and Rufin Vogels1 1 KU Leuven, Belgium Neurons in macaque inferior temporal (IT) cortex, the end stage of the ventral visual stream, show a decrease in the response with stimulus repetition, known as repetition suppression. Several mechanisms have been proposed to explain this form of adaptation in IT, from firing-rate dependent fatigue to influences of other brain areas. We recorded spiking activity from IT cortex of two monkeys while simultaneously stimulating optically neurons previously transduced with a depolarizing opsin, ChrimsonR, and measured the effect of stimulation on their responses. Photo-stimulation could lead to both an increase and a suppression of a neuron’s firing rate. In the first case, preceding photo-stimulation had no effect on the response to a subsequent visual stimulus with a typical contrast; we observed small suppression of the response to repeated photo-stimulation or when a low-contrast visual stimulus followed photo-stimulation. Units suppressed during photo-stimulation showed a strongly suppressed response to simultaneously presented visual and photo-stimulation (compound stimulus). Using this compound stimulus as adapter produced little or no effect on the response to a subsequent visual stimulus compared with repetition of the same visual stimulus. Together, these results suggest only a small if any contribution of firing-rate dependent mechanisms to repetition suppression in IT. Keywords: Neurophysiology, optogenetic, visual adaptation, Nonhuman primate (NHP), temporal cortex Conference: 13th National Congress of the Belgian Society for Neuroscience , Brussels, Belgium, 24 May - 24 May, 2019. Presentation Type: Poster presentation Topic: Behavioral/Systems Neuroscience Citation: Fabbrini F, Van Den Haute C, De Vitis M, Baekelandt V, Vanduffel W and Vogels R (2019). Probing the mechanisms of adaptation of macaque inferotemporal neurons with optogenetics. Front. Neurosci. Conference Abstract: 13th National Congress of the Belgian Society for Neuroscience . doi: 10.3389/conf.fnins.2019.96.00091 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 10 Apr 2019; Published Online: 27 Sep 2019. * Correspondence: Mx. Francesco Fabbrini, KU Leuven, Leuven, Belgium, francesco.fabbrini@kuleuven.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Francesco Fabbrini Chris Van Den Haute Marina De Vitis Veerle Baekelandt Wim Vanduffel Rufin Vogels Google Francesco Fabbrini Chris Van Den Haute Marina De Vitis Veerle Baekelandt Wim Vanduffel Rufin Vogels Google Scholar Francesco Fabbrini Chris Van Den Haute Marina De Vitis Veerle Baekelandt Wim Vanduffel Rufin Vogels PubMed Francesco Fabbrini Chris Van Den Haute Marina De Vitis Veerle Baekelandt Wim Vanduffel Rufin Vogels Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Searching for visual features that explain response variance of face neurons in inferior temporal cortex.

Despite a large body of research on response properties of neurons in the inferior temporal (IT) cortex, studies to date have not yet produced quantitative feature descriptions that can predict responses to arbitrary objects. This deficit in the research prevents a thorough understanding of object representation in the IT cortex. Here we propose a fragment-based approach for finding quantitative feature descriptions of face neurons in the IT cortex. The development of the proposed method was driven by the assumption that it is possible to recover features from a set of natural image fragments if the set is sufficiently large. To find the feature from the set, we compared object responses predicted from each fragment and responses of neurons to these objects, and search for the fragment that revealed the highest correlation with neural object responses. Prediction of object responses of each fragment was made by normalizing Euclidian distance between the fragment and each object to 0 to 1 such that the smaller distance gives the higher value. The distance was calculated at the space where images were transformed to a local orientation space by a Gabor filter and a local max operation. The method allowed us to find features with a correlation coefficient between predicted and neural responses of 0.68 on average (number of object stimuli, 104) from among 560,000 feature candidates, reliably explaining differential responses among faces as well as a general preference for faces over to non-face objects. Furthermore, predicted responses of the resulting features to novel object images were significantly correlated with neural responses to these images. Identification of features comprising specific, moderately complex combinations of local orientations and colors enabled us to predict responses to upright and inverted faces, which provided a possible mechanism of face inversion effects. (292/300).

Seeing a straight line on a curved surface: decoupling of patterns from surfaces by single IT neurons.

We have no difficulty seeing a straight line on a curved piece of paper, but in fact, doing so requires decoupling the shape of the surface from the pattern itself. Here we report a novel form of invariance in the visual cortex: single neurons in monkey inferior temporal cortex respond similarly to congruent transformations of patterns and surfaces, in effect decoupling patterns from the surface on which they are overlaid.

Encoding of Stimulus Probability in Macaque Inferior Temporal Cortex

Optimal perceptual decisions require sensory signals to be combined with prior information about stimulus probability. Although several theories propose that probabilistic information about stimulus occurrence is encoded in sensory cortex, evidence from neuronal recordings has not yet fully supported this view. We recorded activity from single neurons ininferior temporal cortex (IT) while monkeys performed a task that involved discriminating degraded images of faces and fruit. The relative probability of the cue being a face versus a fruit was manipulated by a latent variable that was not revealed to the monkeys and that changed unpredictably over the course of each recording session. In addition to responding to stimulus identity (face or fruit), population responses in IT encoded the long-term stimulus probability of whether a face or a fruit stimulus was more likely to occur. Face-responsive neurons showed reduced firing rates to expected faces, an effect consistent with "expectation suppression," but expected stimuli were decoded from multivariate population signals with greater accuracy. These findings support "predictive coding" theories, whereby neural signals in the mammalian visual system actively encode and update predictions about the local sensory environment.

Divisive Normalization Predicts Adaptation-Induced Response Changes in Macaque Inferior Temporal Cortex.

Stimulus repetition alters neural responses to the repeated stimulus. This so-called adaptation phenomenon has been commonly observed at multiple spatial and temporal scales and in different brain areas, and has been hypothesized to affect the neural representation of the sensory input. Yet, the neural mechanisms underlying adaptation still remain unclear, especially in higher-order cortical areas. Here we employ a divisive normalization model of neural responses to predict adaptation-induced changes in responses of single neurons in the macaque inferior temporal (IT) cortex. According to this model, the response of a neuron is determined by an interplay between its direct excitatory and divisive normalizing inputs, with each input being subject to adaptation. To test the model, we recorded the responses of single IT cortex neurons to complex visual stimuli while separately adapting the two putative types of input to those neurons. We compared the changes in responses of these neurons following such adaptation with predictions derived from the divisive normalization model. As predicted by the model, we show that adaptation in the IT cortex can, depending on the relative strength of each putative type of input to a neuron, suppress or enhance the neural response to a complex stimulus. More generally, our data suggest that adaptation serves to selectively enhance processing of the stimuli that differ from recently experienced ones, even when these occur within a configuration of multiple stimuli. Stimulus repetition alters neural responses to the repeated stimulus. This so-called adaptation phenomenon has been robustly demonstrated in brains of different species and is considered to be a form of short-term plasticity inherent to the processing of sensory stimuli. Nevertheless, the functional role and underlying mechanisms of adaptation remain unclear. Here we demonstrate that divisive normalization, a canonical neural computation operating throughout the brain, predicts the adaptation-induced changes in response of single neurons to complex stimulus configurations in the macaque inferotemporal cortex. Our findings embed adaptation effects of inferotemporal neurons into the context of a broader neural network perspective that includes divisive normalization. Additionally, our findings have implications for understanding of the function of adaptation in higher-order sensory cortices.

The impact of orientation filtering on face-selective neurons in monkey inferior temporal cortex.

Faces convey complex social signals to primates. These signals are tolerant of some image transformations (e.g. changes in size) but not others (e.g. picture-plane rotation). By filtering face stimuli for orientation content, studies of human behavior and brain responses have shown that face processing is tuned to selective orientation ranges. In the present study, for the first time, we recorded the responses of face-selective neurons in monkey inferior temporal (IT) cortex to intact and scrambled faces that were filtered to selectively preserve horizontal or vertical information. Guided by functional maps, we recorded neurons in the lateral middle patch (ML), the lateral anterior patch (AL), and an additional region located outside of the functionally defined face-patches (CONTROL). We found that neurons in ML preferred horizontal-passed faces over their vertical-passed counterparts. Neurons in AL, however, had a preference for vertical-passed faces, while neurons in CONTROL had no systematic preference. Importantly, orientation filtering did not modulate the firing rate of neurons to phase-scrambled face stimuli in any recording region. Together these results suggest that face-selective neurons found in the face-selective patches are differentially tuned to orientation content, with horizontal tuning in area ML and vertical tuning in area AL.

Dietary high cholesterol and trace metals in the drinking water increase levels of ABCA1 in the rabbit hippocampus and temporal cortex.

Cholesterol-fed rabbits have been documented to show increased amyloid-β (Aβ) deposits in the brain that can be exacerbated by the quality of drinking water especially if rabbits drink tap water or distilled water containing copper. One mechanism of cholesterol and Aβ clearance may be through the ATP-binding cassette transporter A1 (ABCA1). Using an ABCA1 antibody, we determined the number of ABCA1-immunopositive neurons in three areas of rabbit brain as a function of feeding 2% cholesterol and providing tap water, distilled water, or distilled water to which aluminum, copper, or zinc was added. The number of neurons with ABCA1 immunoreactivity was increased significantly as a result of dietary cholesterol in the rabbit hippocampus and inferior and superior temporal cortex. The number of neurons with ABCA1 immunoreactivity was further increased in all three areas as a result of cholesterol-fed rabbits drinking tap water or distilled water with copper. Finally, cholesterol-fed rabbits that drank distilled water with aluminum also showed an increased number of ABCA1-immunopositive neurons in inferior and superior temporal cortex. These data suggest that ABCA1 levels increase in parallel with previously documented increases in Aβ levels as a result of high dietary cholesterol and copper in the drinking water. Addition of aluminum to distilled water may have a similar effect in the temporal cortex. ABCA1 has been proposed as a means of clearing Aβ from the brain and manipulations that increase Aβ also result in an increase of clearance machinery.

Simple Learned Weighted Sums of Inferior Temporal Neuronal Firing Rates Accurately Predict Human Core Object Recognition Performance.

To go beyond qualitative models of the biological substrate of object recognition, we ask: can a single ventral stream neuronal linking hypothesis quantitatively account for core object recognition performance over a broad range of tasks? We measured human performance in 64 object recognition tests using thousands of challenging images that explore shape similarity and identity preserving object variation. We then used multielectrode arrays to measure neuronal population responses to those same images in visual areas V4 and inferior temporal (IT) cortex of monkeys and simulated V1 population responses. We tested leading candidate linking hypotheses and control hypotheses, each postulating how ventral stream neuronal responses underlie object recognition behavior. Specifically, for each hypothesis, we computed the predicted performance on the 64 tests and compared it with the measured pattern of human performance. All tested hypotheses based on low- and mid-level visually evoked activity (pixels, V1, and V4) were very poor predictors of the human behavioral pattern. However, simple learned weighted sums of distributed average IT firing rates exactly predicted the behavioral pattern. More elaborate linking hypotheses relying on IT trial-by-trial correlational structure, finer IT temporal codes, or ones that strictly respect the known spatial substructures of IT ("face patches") did not improve predictive power. Although these results do not reject those more elaborate hypotheses, they suggest a simple, sufficient quantitative model: each object recognition task is learned from the spatially distributed mean firing rates (100 ms) of ∼60,000 IT neurons and is executed as a simple weighted sum of those firing rates. Significance statement: We sought to go beyond qualitative models of visual object recognition and determine whether a single neuronal linking hypothesis can quantitatively account for core object recognition behavior. To achieve this, we designed a database of images for evaluating object recognition performance. We used multielectrode arrays to characterize hundreds of neurons in the visual ventral stream of nonhuman primates and measured the object recognition performance of >100 human observers. Remarkably, we found that simple learned weighted sums of firing rates of neurons in monkey inferior temporal (IT) cortex accurately predicted human performance. Although previous work led us to expect that IT would outperform V4, we were surprised by the quantitative precision with which simple IT-based linking hypotheses accounted for human behavior.

Invariant visual object recognition: biologically plausible approaches.

Key properties of inferior temporal cortex neurons are described, and then, the biological plausibility of two leading approaches to invariant visual object recognition in the ventral visual system is assessed to investigate whether they account for these properties. Experiment 1 shows that VisNet performs object classification with random exemplars comparably to HMAX, except that the final layer C neurons of HMAX have a very non-sparse representation (unlike that in the brain) that provides little information in the single-neuron responses about the object class. Experiment 2 shows that VisNet forms invariant representations when trained with different views of each object, whereas HMAX performs poorly when assessed with a biologically plausible pattern association network, as HMAX has no mechanism to learn view invariance. Experiment 3 shows that VisNet neurons do not respond to scrambled images of faces, and thus encode shape information. HMAX neurons responded with similarly high rates to the unscrambled and scrambled faces, indicating that low-level features including texture may be relevant to HMAX performance. Experiment 4 shows that VisNet can learn to recognize objects even when the view provided by the object changes catastrophically as it transforms, whereas HMAX has no learning mechanism in its S–C hierarchy that provides for view-invariant learning. This highlights some requirements for the neurobiological mechanisms of high-level vision, and how some different approaches perform, in order to help understand the fundamental underlying principles of invariant visual object recognition in the ventral visual stream.Electronic supplementary materialThe online version of this article (doi:10.1007/s00422-015-0658-2) contains supplementary material, which is available to authorized users.

Perturbation of Posterior Inferior Temporal Cortical Activity Impairs Coarse Orientation Discrimination.

It is reasonable to assume that the discrimination of simple visual stimuli depends on the activity of early visual cortical neurons, because simple visual features are supposedly coded in these areas whereas more complex features are coded in late visual areas. Recently, we showed that training monkeys in a coarse orientation discrimination task modified the response properties of single neurons in the posterior inferior temporal (PIT) cortex, a late visual area. Here, we examined the contribution of PIT to coarse orientation discrimination using causal perturbation methods. Electrical stimulation (ES) of PIT with currents of at least 100 µA impaired coarse orientation discrimination in monkeys. The performance deterioration did not exclusively reflect a general impairment to perform a difficult perceptual task. However, high current (650 µA) but not low-current (100 µA) ES also impaired fine color discrimination. ES of temporal regions dorsal or anterior to PIT produced less impairment of coarse orientation discrimination than ES of PIT. Injections of the GABA agonist muscimol into PIT also impaired performance. These data suggest that the late cortical area PIT is part of the network that supports coarse orientation discrimination of a simple grating stimulus, at least after extensive training in this task at threshold.

Correlated activity supports efficient cortical processing.

Visual recognition is a computational challenge that is thought to occur via efficient coding. An important concept is sparseness, a measure of coding efficiency. The prevailing view is that sparseness supports efficiency by minimizing redundancy and correlations in spiking populations. Yet, we recently reported that “choristers”, neurons that behave more similarly (have correlated stimulus preferences and spontaneous coincident spiking), carry more generalizable object information than uncorrelated neurons (“soloists”) in macaque inferior temporal (IT) cortex. The rarity of choristers (as low as 6% of IT neurons) indicates that they were likely missed in previous studies. Here, we report that correlation strength is distinct from sparseness (choristers are not simply broadly tuned neurons), that choristers are located in non-granular output layers, and that correlated activity predicts human visual search efficiency. These counterintuitive results suggest that a redundant correlational structure supports efficient processing and behavior.

Finding and recognizing objects in natural scenes: complementary computations in the dorsal and ventral visual systems.

Searching for and recognizing objects in complex natural scenes is implemented by multiple saccades until the eyes reach within the reduced receptive field sizes of inferior temporal cortex (IT) neurons. We analyze and model how the dorsal and ventral visual streams both contribute to this. Saliency detection in the dorsal visual system including area LIP is modeled by graph-based visual saliency, and allows the eyes to fixate potential objects within several degrees. Visual information at the fixated location subtending approximately 9° corresponding to the receptive fields of IT neurons is then passed through a four layer hierarchical model of the ventral cortical visual system, VisNet. We show that VisNet can be trained using a synaptic modification rule with a short-term memory trace of recent neuronal activity to capture both the required view and translation invariances to allow in the model approximately 90% correct object recognition for 4 objects shown in any view across a range of 135° anywhere in a scene. The model was able to generalize correctly within the four trained views and the 25 trained translations. This approach analyses the principles by which complementary computations in the dorsal and ventral visual cortical streams enable objects to be located and recognized in complex natural scenes.

Repetition suppression in macaque superior temporal sulcus (STS) for dynamic visual stimuli depicting hand actions.

Repetition suppression in macaque superior temporal sulcus (STS) for dynamic visual stimuli depicting hand actions.