Effects of attention and stimulus interaction on visual responses of inferior temporal neurons in macaque

1988 ◽  
Vol 60 (1) ◽  
pp. 344-364 ◽  
Author(s):  
T. Sato
Keyword(s):  
Visual Field ◽  
Receptive Field ◽  
Discrimination Task ◽  
Temporal Cortex ◽  
Pattern Discrimination ◽  
Suppressive Effect ◽  
Neutral Stimulus ◽  
Inferior Temporal Cortex ◽  
Visual Response ◽  
Visual Responses

1. Extracellular discharges were recorded from neurons in the inferior temporal cortex (area TE) of three macaque monkeys while they performed visual fixation and pattern discrimination tasks. For the pattern discrimination task, monkey was trained to release the lever quickly at the onset of one of two pattern stimuli and to release the lever at the dimming of the other pattern. During this task, neutral light stimulus (light bar) to which the monkey was not required to respond was presented once a trial either prior to the onset of the discriminandum or during presentation of the pattern that dimmed later. The neuronal activities evoked by the neutral stimulus under these two conditions were compared. 2. When the discriminanda were located at the center or at 5 degrees in the contralateral visual field, one-half of the neurons showed significantly smaller responses to the neutral stimulus when it was presented during presentation of the dimming pattern than when it was presented prior to the onset of the discriminandum. 3. The suppressive effect depended on the location of the two stimuli. When the neutral stimulus was located in the ipsilateral visual field and the pattern was located in the contralateral visual field, the response to the neutral stimulus was suppressed. However, when the pattern was located in the ipsilateral visual field (5 degrees visual angle), still within the receptive field for many neurons, the suppressive effect of the pattern on the response to the neutral stimulus in the contralateral visual field was almost undetectable. 4. When the pattern was located nearer the fovea than was the neutral stimulus, the suppressive effect was greater than when the pattern was located more peripherally to the neutral stimulus. Different from the receptive field of more primary visual neurons, this suppressive effect did not appear to be related to the neuron's responsiveness to the patterns nor to precise stimulus location in the receptive field. 5. The magnitude of suppression by the attended pattern on the visual response during the pattern discrimination task correlated with the suppression noted in the presence of a fixation spot during the fixation tasks, while the animals did not fixate on the attended pattern. The response of some neurons to the neutral stimulus prior to pattern presentation during the pattern discrimination task was enhanced slightly compared with the response recorded during the simple fixation task.(ABSTRACT TRUNCATED AT 400 WORDS)

Enhancement of inferior temporal neurons during visual discrimination

1987 ◽  
Vol 58 (6) ◽  
pp. 1292-1306 ◽  
Author(s):  
B. J. Richmond ◽  
T. Sato
Keyword(s):  
Spatial Attention ◽  
Trial Type ◽  
Discrimination Task ◽  
Temporal Cortex ◽  
Pattern Discrimination ◽  
Response Strength ◽  
The Other ◽  
Inferior Temporal Cortex ◽  
Attention Task ◽  
Type Pattern

1. Previous results have shown that spatially directed attention enhances the stimulus-elicited responses of neurons in some areas of the brain. In the inferior temporal (IT) cortex, however, directing attention toward a stimulus mildly inhibits the responses of the neurons. Inferior temporal cortex is involved in pattern discrimination, but not spatial localization. If enhancement signifies that a neuron is participating in the function for which that part of cortex is responsible, then pattern discrimination, not spatial attention, should enhance responses of IT neurons. The influence of pattern discrimination behavior on the responses of IT neurons was therefore compared with previously reported suppressive influences of both spatial attention and the fixation point. 2. Single IT neurons were recorded from two monkeys while they performed each of five tasks. One task required the monkey to make a pattern discrimination between a bar and a square of light. In the other four tasks the same bar of light appeared, but the focus of spatial attention could differ, and the fixation point could be present or absent. Either attention to (without discrimination of) the bar stimulus or the presence of the fixation point attenuated responses slightly. These two suppressive influences produced a greater attenuation when both were present. 3. The visual conditions and motor requirements when the bar stimulus appeared in the discrimination task were identical to those of the trials in the stimulus attention task. However, one-half of the responsive neurons showed significantly stronger responses to the bar stimulus when it appeared in the discrimination task than when it appeared in the stimulus attention task. For most of these neurons, discrimination just overcame the combined effect of the two suppressive influences. For six other neurons, the response strength was significantly greater during the discrimination task than during any other task. 4. The monkeys achieved an overall correct performance rate of 90% in both the discrimination and stimulus attention tasks. To achieve this performance in the discrimination task they adopted a strategy in which they performed one trial type, bar stimulus attention trials, perfectly (100%) and the other trial type, pattern trials, relatively poorly (84% correct).(ABSTRACT TRUNCATED AT 400 WORDS)

Organization of local horizontal functional interactions between neurons in the inferior temporal cortex of macaque monkeys

2014 ◽  
Vol 111 (12) ◽  
pp. 2589-2602 ◽  
Author(s):  
Hiroshi Tamura ◽  
Yoshiya Mori ◽  
Hidekazu Kaneko
Keyword(s):  
Neuronal Activity ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Visual Object ◽  
Detailed Knowledge ◽  
Visual Response ◽  
Stimulus Preference ◽  
Macaque Monkeys ◽  
Functional Interactions ◽  
Cross Correlation Analysis

Detailed knowledge of neuronal circuitry is necessary for understanding the mechanisms underlying information processing in the brain. We investigated the organization of horizontal functional interactions in the inferior temporal cortex of macaque monkeys, which plays important roles in visual object recognition. Neuronal activity was recorded from the inferior temporal cortex using an array of eight tetrodes, with spatial separation between paired neurons up to 1.4 mm. We evaluated functional interactions on a time scale of milliseconds using cross-correlation analysis of neuronal activity of the paired neurons. Visual response properties of neurons were evaluated using responses to a set of 100 visual stimuli. Adjacent neuron pairs tended to show strong functional interactions compared with more distant neuron pairs, and neurons with similar stimulus preferences tended to show stronger functional interactions than neurons with different stimulus preferences. Thus horizontal functional interactions in the inferior temporal cortex appear to be organized according to both cortical distances and similarity in stimulus preference between neurons. Furthermore, the relationship between strength of functional interactions and similarity in stimulus preference observed in distant neuron pairs was more prominent than in adjacent pairs. The results suggest that functional circuitry is specifically organized, depending on the horizontal distances between neurons. Such specificity endows each circuit with unique functions.

A Theoretical Basis for Emergent Pattern Discrimination in Neural Systems Through Slow Feature Extraction

2010 ◽  
Vol 22 (12) ◽  
pp. 2979-3035 ◽  
Author(s):  
Stefan Klampfl ◽  
Wolfgang Maass
Keyword(s):  
Feature Extraction ◽  
Theoretical Basis ◽  
Learning Algorithm ◽  
Temporal Cortex ◽  
Pattern Discrimination ◽  
Stimulus Onset ◽  
Inferior Temporal Cortex ◽  
Linear Discriminant ◽  
Discrimination Capability ◽  
The Brain

Neurons in the brain are able to detect and discriminate salient spatiotemporal patterns in the firing activity of presynaptic neurons. It is open how they can learn to achieve this, especially without the help of a supervisor. We show that a well-known unsupervised learning algorithm for linear neurons, slow feature analysis (SFA), is able to acquire the discrimination capability of one of the best algorithms for supervised linear discrimination learning, the Fisher linear discriminant (FLD), given suitable input statistics. We demonstrate the power of this principle by showing that it enables readout neurons from simulated cortical microcircuits to learn without any supervision to discriminate between spoken digits and to detect repeated firing patterns that are embedded into a stream of noise spike trains with the same firing statistics. Both these computer simulations and our theoretical analysis show that slow feature extraction enables neurons to extract and collect information that is spread out over a trajectory of firing states that lasts several hundred ms. In addition, it enables neurons to learn without supervision to keep track of time (relative to a stimulus onset, or the initiation of a motor response). Hence, these results elucidate how the brain could compute with trajectories of firing states rather than only with fixed point attractors. It also provides a theoretical basis for understanding recent experimental results on the emergence of view- and position-invariant classification of visual objects in inferior temporal cortex.

Response properties of neurons in temporal cortical visual areas of infant monkeys

1993 ◽  
Vol 70 (3) ◽  
pp. 1115-1136 ◽  
Author(s):  
H. R. Rodman ◽  
S. P. Scalaidhe ◽  
C. G. Gross
Keyword(s):  
Nitrous Oxide ◽  
Temporal Cortex ◽  
Receptive Fields ◽  
Stimulus Presentation ◽  
Pattern Perception ◽  
Inferior Temporal Cortex ◽  
Field Size ◽  
Visual Response ◽  
Control Adult ◽  
Oxide Anesthesia

1. Inferior temporal cortex (IT) is a "high-order" region of primate temporal visual cortex implicated in visual pattern perception and recognition. To gain some insight into the development of this area, we compared the properties of single neurons in IT in infant monkeys ranging from 5 wk to 7 mo of age with those of neurons in IT in adult animals. Both anesthetized and awake behaving paradigms were used. 2. In immobilized infant monkeys under nitrous oxide anesthesia, the incidence of visually responsive cells was markedly less than in adult monkeys studied under similar conditions. In infants 4-7 mo of age, only half of IT neurons studied were visually responsive, compared with > 80% in adult monkeys. In monkeys < 4 mo old, even fewer (< 10%) could be visually driven. "Habituation" of IT cells to repeated stimulus presentation appeared more pronounced in infant monkeys under nitrous oxide anesthesia than in adult animals. 3. IT cells in the anesthetized infant monkeys that did respond showed receptive field properties similar to those of responsive adult IT neurons studied under similar conditions. Two thirds of the receptive fields plotted in the anesthetized 4 to 7-mo-old group were bilateral, and median field size did not differ between the infants and comparable adult groups, being approximately 20 degrees on a side in each case. 4. In contrast to the results obtained under anesthesia, most IT cells in alert infant monkeys 5 wk-7 mo of age (80%) were responsive to visual stimuli, and this incidence of visually responsive IT neurons did not differ from that obtained in awake adult macaques. However, response magnitude, measured as spikes per second above baseline rate, was significantly lower in the infant alert sample than in the adult control (5.2 vs. 12.6 spikes/s, mean +/- SE, deviation from spontaneous rate, respectively). 5. In addition to having lower magnitudes of visual response, IT cells in the awake infants also tended to have longer and more variable latencies. The overall mean for the infant cells was 196 ms, compared with an overall mean of 140 ms for IT neurons in the alert control adult. 6. Although the magnitude of response of neurons in alert infant IT cortex was lower overall, the incidence and features of stimulus selectivity shown by alert infant IT neurons were strikingly similar to those of IT cells of both anesthetized and unanesthetized adult monkeys.(ABSTRACT TRUNCATED AT 400 WORDS)

Visual Responses of the Human Superior Colliculus: A High-Resolution Functional Magnetic Resonance Imaging Study

2005 ◽  
Vol 94 (4) ◽  
pp. 2491-2503 ◽  
Author(s):  
Keith A. Schneider ◽  
Sabine Kastner
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
High Resolution ◽  
Superior Colliculus ◽  
Visual Fields ◽  
Visual Response ◽  
Visual Responses ◽  
Subcortical Structures ◽  
Stimulus Motion ◽  
Low Contrast

The superior colliculus (SC) is a multimodal laminar structure located on the roof of the brain stem. The SC is a key structure in a distributed network of areas that mediate saccadic eye movements and shifts of attention across the visual field and has been extensively studied in nonhuman primates. In humans, it has proven difficult to study the SC with functional MRI (fMRI) because of its small size, deep location, and proximity to pulsating vascular structures. Here, we performed a series of high-resolution fMRI studies at 3 T to investigate basic visual response properties of the SC. The retinotopic organization of the SC was determined using the traveling wave method with flickering checkerboard stimuli presented at different polar angles and eccentricities. SC activations were confined to stimulation of the contralateral hemifield. Although a detailed retinotopic map was not observed, across subjects, the upper and lower visual fields were represented medially and laterally, respectively. Responses were dominantly evoked by stimuli presented along the horizontal meridian of the visual field. We also measured the sensitivity of the SC to luminance contrast, which has not been previously reported in primates. SC responses were nearly saturated by low contrast stimuli and showed only small response modulation with higher contrast stimuli, indicating high sensitivity to stimulus contrast. Responsiveness to stimulus motion in the SC was shown by robust activations evoked by moving versus static dot stimuli that could not be attributed to eye movements. The responses to contrast and motion stimuli were compared with those in the human lateral geniculate nucleus. Our results provide first insights into basic visual responses of the human SC and show the feasibility of studying subcortical structures using high-resolution fMRI.

scholarly journals Attractor dynamics in networks with learning rules inferred from in vivo data

2017 ◽  
Author(s):  
Ulises Pereira ◽  
Nicolas Brunel
Keyword(s):  
Neural Network ◽  
Hebbian Learning ◽  
Temporal Cortex ◽  
Memory Storage ◽  
Inferior Temporal Cortex ◽  
Association Cortex ◽  
Visual Responses ◽  
Neural Network Models ◽  
Firing Rates ◽  
Learning Rules

AbstractThe attractor neural network scenario is a popular scenario for memory storage in association cortex, but there is still a large gap between models based on this scenario and experimental data. We study a recurrent network model in which both learning rules and distribution of stored patterns are inferred from distributions of visual responses for novel and familiar images in inferior temporal cortex (ITC). Unlike classical attractor neural network models, our model exhibits graded activity in retrieval states, with distributions of firing rates that are close to lognormal. Inferred learning rules are close to maximizing the number of stored patterns within a family of unsupervised Hebbian learning rules, suggesting learning rules in ITC are optimized to store a large number of attractor states. Finally, we show that there exists two types of retrieval states: one in which firing rates are constant in time, another in which firing rates fluctuate chaotically.

scholarly journals Visuospatial coding in primate prefrontal neurons revealed by oculomotor paradigms

1990 ◽  
Vol 63 (4) ◽  
pp. 814-831 ◽  
Author(s):  
S. Funahashi ◽  
C. J. Bruce ◽  
P. S. Goldman-Rakic
Keyword(s):  
Prefrontal Cortex ◽  
Visual Field ◽  
Visual Cues ◽  
Neuron Activity ◽  
Delayed Response ◽  
Visual Response ◽  
Visual Responses ◽  
Directional Tuning ◽  
Vertical Meridian ◽  
Visual Probe

1. Visual responses and their relationship to delay-period activity were studied by recording single neuron activity from the prefrontal cortex of rhesus monkeys while they performed an oculomotor delayed-response (ODR) and a visual probe (VP) task. In the ODR task, the monkey was required to maintain fixation of a central spot of light throughout the cue (0.5 s) and delay (3 s) periods and then make a saccadic eye movement to one of four or eight locations where the visual cue had been presented. In the VP task, the same visual stimuli that were used in the ODR task were presented for 0.5 s, but no response was required. The VP task was thus employed to test the passive visual response and, by comparison with cue-elicited activity in the ODR task, to examine the degree of behavioral enhancement present in prefrontal visual activity. 2. Among 434 neurons recorded from the prefrontal cortex within and surrounding the principal sulcus (PS), 261 had task-related activity during at least one phase of the ODR task, and 74 of these had phasic visual responses to the onset of the visual cues with a median latency of 116 ms. The visual responses of 69 neurons were excitatory, and 5 neurons were inhibited. Five of the neurons with excitatory visual responses also responded transiently after the offset of the cue. 3. Visual responses were classified as directional for 71 PS neurons (96%) in that excitatory or inhibitory responses occurred only for location of cues in a restricted portion of the visual field. Only 3 PS neurons were omnidirectional, i.e., responded equivalently to cues in all locations tested. 4. The best direction and tuning specificity of all PS neurons with directional visual responses were estimated from parameters yielding the best fit to a Gaussian-shaped tuning function. The best direction for the majority (71%) of neurons was toward the visual field contralateral to the hemisphere where the neuron was located. The remaining neurons had their best directions in the ipsilateral field (18%) or along the vertical meridian (11%). 5. The specificity of directional tuning for PS visual responses was quite variable, ranging from neurons that responded only to one of the eight cue locations to neurons that responded to all eight, but in a clearly graded fashion. The standard deviation parameter of the Gaussian curve indexed the breadth of directional tuning of each neuron; its median value was 37 degrees.(ABSTRACT TRUNCATED AT 400 WORDS)

Disparity-Selective Neurons in Area V4 of Macaque Monkeys

2002 ◽  
Vol 87 (4) ◽  
pp. 1960-1973 ◽  
Author(s):  
Masayuki Watanabe ◽  
Hiroki Tanaka ◽  
Takanori Uka ◽  
Ichiro Fujita
Keyword(s):  
Receptive Field ◽  
Binocular Disparity ◽  
Temporal Cortex ◽  
Intermediate Stage ◽  
Visual Pathway ◽  
Inferior Temporal Cortex ◽  
Tuning Curves ◽  
Area V4 ◽  
Ventral Visual Pathway ◽  
V4 Neurons

Area V4 is an intermediate stage of the ventral visual pathway providing major input to the final stages in the inferior temporal cortex (IT). This pathway is involved in the processing of shape, color, and texture. IT neurons are also sensitive to horizontal binocular disparity, suggesting that binocular disparity is processed along the ventral visual pathway. In the present study, we examined the processing of binocular disparity information by V4 neurons. We recorded responses of V4 neurons to binocularly disparate stimuli. A population of V4 neurons modified their responses according to changes of stimulus disparity; neither monocular responses nor eye movements could account for this modulation. Disparity-tuning curves were similar for different locations within a neuron's receptive field. Neighboring neurons recorded using a single electrode displayed similar disparity-tuning properties. These findings indicate that a population of V4 neurons is selective for binocular disparity, invariant for the position of the stimulus within the receptive field. The finding that V4 neurons with similar disparity selectivity are clustered suggests the existence of functional modules for disparity processing in V4.

scholarly journals Attentional Modulation of Visual Responses by Flexible Input Gain

2009 ◽  
Vol 101 (4) ◽  
pp. 2089-2106 ◽  
Author(s):  
Geoffrey M. Ghose
Keyword(s):  
Receptive Field ◽  
Spatial Attention ◽  
Sensory Integration ◽  
Suppressive Effect ◽  
Common Mechanism ◽  
Visual Responses ◽  
Attentional Modulation ◽  
Low Contrast ◽  
Imaging Results ◽  
Input Gain

Although it is clear that sensory responses in the cortex can be strongly modulated by stimuli outside of classical receptive fields as well as by extraretinal signals such as attention and anticipation, the exact rules governing the neuronal integration of sensory and behavioral signals remain unclear. For example, most experiments studying sensory interactions have not explored attention, while most studies of attention have relied on the responses to relatively limited sets of stimuli. However, a recent study of V4 responses, in which location, orientation, and spatial attention were systematically varied, suggests that attention can both facilitate and suppress specific sensory inputs to a neuron according to behavioral relevance. To explore the implications of such input gain, we modeled the effects of a center-surround organization of attentional modulation using existing receptive field models of sensory integration. The model is consistent with behavioral measurements of a suppressive effect that surrounds the facilitatory locus of spatial attention. When this center-surround modulation is incorporated into realistic models of sensory integration, it is able to explain seemingly disparate observations of attentional effects in the neurophysiological literature, including spatial shifts in receptive field position and the preferential modulation of low contrast stimuli. The model is also consistent with recent formulations of attention to features in which gain is variably applied among cells with different receptive field properties. Consistent with functional imaging results, the model predicts that spatial attention effects will vary between different visual areas and suggests that attention may act through a common mechanism of selective and flexible gain throughout the visual system.

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