Neural Correlates of Fine Depth Discrimination in Monkey Inferior Temporal Cortex

Uka, Takanori; Tanabe, Seiji; Watanabe, Masayuki; Fujita, Ichiro

doi:10.1523/jneurosci.1637-05.2005

Cited by 91 publications

(68 citation statements)

References 36 publications

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“…Our microstimulation results add support for the bottom-up direction of the relationship of V4 neurons with perceptual decisions. Uka et al (2005) reported that neurons in the IT show choicepredictive activity 360 ms after stimulus onset. This is three times the latency of the visual response, or the latency of disparity selectivity (Uka et al, 2005).…”

Section: Latency Of Choice-predictive Activity During Fine Disparity mentioning

confidence: 99%

“…Uka et al (2005) reported that neurons in the IT show choicepredictive activity 360 ms after stimulus onset. This is three times the latency of the visual response, or the latency of disparity selectivity (Uka et al, 2005). The increase in the delay of the choicepredictive activity from V4 to IT (230 ms) is disproportionate to the increase in the delay of the visual response or the disparity selectivity (ϳ20 ms) (Watanabe et al, 2002;Tanabe et al, 2004;Uka et al, 2005).…”

Section: Latency Of Choice-predictive Activity During Fine Disparity mentioning

confidence: 99%

“…Microstimulation and inactivation have not provided a causal link between neural activity in MT and discrimination of fine disparity (Uka and DeAngelis, 2006;Chowdhury and DeAngelis, 2008). In contrast, the inferior temporal cortex (IT) is related to fine disparity discrimination because trial-by-trial fluctuations of neuronal responses are correlated with perceptual decisions about subthreshold disparity (Uka et al, 2005). But the decision-related activity emerged substantially late (360 ms) after the stimulus onset, suggesting that the decision-related activity reflects modulation in the top-down direction, e.g., decision signals modulating sensory signals, rather than sensory signals driving decisions in the bottom-up direction.…”

Section: Introductionmentioning

confidence: 99%

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Neural Activity in Cortical Area V4 Underlies Fine Disparity Discrimination

Shiozaki

Tanabe²,

Doi³

et al. 2012

J. Neurosci.

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Primates are capable of discriminating depth with remarkable precision using binocular disparity. Neurons in area V4 are selective for relative disparity, which is the crucial visual cue for discrimination of fine disparity. Here, we investigated the contribution of V4 neurons to fine disparity discrimination. Monkeys discriminated whether the center disk of a dynamic random-dot stereogram was in front of or behind its surrounding annulus. We first behaviorally tested the reference frame of the disparity representation used for performing this task. After learning the task with a set of surround disparities, the monkey generalized its responses to untrained surround disparities, indicating that the perceptual decisions were generated from a disparity representation in a relative frame of reference. We then recorded single-unit responses from V4 while the monkeys performed the task. On average, neuronal thresholds were higher than the behavioral thresholds. The most sensitive neurons reached thresholds as low as the psychophysical thresholds. For subthreshold disparities, the monkeys made frequent errors. The variable decisions were predictable from the fluctuation in the neuronal responses. The predictions were based on a decision model in which each V4 neuron transmits the evidence for the disparity it prefers. We finally altered the disparity representation artificially by means of microstimulation to V4. The decisions were systematically biased when microstimulation boosted the V4 responses. The bias was toward the direction predicted from the decision model. We suggest that disparity signals carried by V4 neurons underlie precise discrimination of fine stereoscopic depth.

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Section: Latency Of Choice-predictive Activity During Fine Disparity mentioning

confidence: 99%

Section: Latency Of Choice-predictive Activity During Fine Disparity mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Neural Activity in Cortical Area V4 Underlies Fine Disparity Discrimination

Shiozaki

Tanabe²,

Doi³

et al. 2012

J. Neurosci.

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“…These observations may reflect a causal link between the activity of single neurons and sensory decisions. Several groups quantified these correlations with choice probabilities (CPs), allowing comparison across cortical areas (Celebrini and Newsome, 1994;Britten et al, 1996;Uka et al, 2005) and visual tasks Dodd et al, 2001;Uka and DeAngelis, 2004;Purushothaman and Bradley, 2005;Uka et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Macaque V2 Neurons, But Not V1 Neurons, Show Choice-Related Activity

Nienborg¹,

Cumming²

2006

J. Neurosci.

135

144

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In the macaque extrastriate cortex, robust correlations between perceptual choice and neuronal response have been demonstrated, frequently quantified as choice probabilities (CPs). Such correlations are modest in early visual cortex, suggesting that CPs may depend on the position of a neuron in the hierarchy of visual processing. However, previous studies have not compared neurons with similar precision in equivalent tasks.We investigated the role of cortical hierarchy on CP using a task for which significant CPs have been described previously for middle temporal area (MT). We measured CPs in disparity-selective neurons from both V1 and V2. The stimulus was a dynamic random dot stereogram, presented with a near or a far disparity, masked by varying numbers of binocularly uncorrelated dots. Two macaque monkeys reported whether they perceived a circular patch in front or behind a surrounding annulus in a forced choice task.For V2 (n ϭ 69), CP was on average 0.56, the first demonstration of systematic CPs in a visual area as early as V2. In V1 (n ϭ 74), average CP was at chance level (0.51). The pattern was similar in a subgroup of neurons selected such that the statistical precision in the task was on average identical to that reported for MT (mean CP, 0.51 for V1, n ϭ 33; 0.58 for V2, n ϭ 54). This difference between V1 and V2 could not be explained by eye movements, stimulus size relative to the receptive field, or differences in disparity tuning. Rather, it seems to reflect a functional difference (at least in disparity processing) between striate and extrastriate cortex.

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“…One method that has been widely used to suggest that signals from particular neurons contribute to a given perceptual decision combines threshold psychophysics with single-unit recordings. A trialto-trial correlation between neuronal activity and perceptual judgment, which cannot be explained by the visual stimulus, is taken as evidence that neuronal signals contribute to a decision [1][2][3][4][5][6][7] . Such correlation, often quantified by 'choice probability', should then also depend on the task strategy employed by the subject 6 .…”

Section: Introductionmentioning

confidence: 99%

Psychophysically measured task strategy for disparity discrimination is reflected in V2 neurons

Nienborg

Cumming

2007

Nat Neurosci

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In perceptual tasks, subjects attempt to rely on their most informative cues. Such strategic choices should be reflected in the types of sensory neurons used. We investigated this in a binocular disparity discrimination task. Using psychophysical reverse-correlation, also known as image classification, we identified the perceptual strategy in two macaques. Correlation between reported disparity sign and disparity noise samples on each trial yielded detection 'filters'. Filter amplitude at near disparities exceeded that at far disparities, indicating that the subjects relied more on near disparities. Recordings from both macaques' disparity-selective V2 neurons showed correlation between neuronal responses and perceptual judgment in near-preferring, not far-preferring units, mirroring the psychophysically measured strategy. After one monkey learned to weight near and far disparities equally, activity in its far-preferring neurons correlated with choice. Thus, the pattern of correlations between neuronal activity and perceptual reports reveals how subjects use their neuronal signals.

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Neural Correlates of Fine Depth Discrimination in Monkey Inferior Temporal Cortex

Cited by 91 publications

References 36 publications

Neural Activity in Cortical Area V4 Underlies Fine Disparity Discrimination

Neural Activity in Cortical Area V4 Underlies Fine Disparity Discrimination

Macaque V2 Neurons, But Not V1 Neurons, Show Choice-Related Activity

Psychophysically measured task strategy for disparity discrimination is reflected in V2 neurons

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