Neural Correlates of Subsecond Time Distortion in the Middle Temporal Area of Visual Cortex

Abstract

How does the brain represent the passage of time at the subsecond scale? Although different conceptual models for time perception have been proposed, its neurophysiological basis remains unknown. We took advantage of a visual duration illusion produced by stimulus novelty to link changes in cortical activity in monkeys with distortions of duration perception in humans. We found that human subjects perceived the duration of a subsecond motion pulse with a novel direction longer than a motion pulse with a repeated direction. Recording from monkeys viewing identical motion stimuli but performing a different behavioral task, we found that both the duration and amplitude of the neural response in the middle temporal area of visual cortex were positively correlated with the degree of novelty of the motion direction. In contrast to previous accounts that attribute distortions in duration perception to changes in the speed of a putative internal clock, our results suggest that the known adaptive properties of neural activity in visual cortex contributes to subsecond temporal distortions.

Subjective Duration as a Signature of Coding Efficiency: Emerging Links Among Stimulus Repetition, Predictive Coding, and Cortical GABA Levels

“…Indirect evidence that subjective duration is correlated with the size of the stimulus-specific neural response has been provided by Sadeghi et al (2011), who presented human participants with a sequence of 200-ms pulses of dot motion stimuli followed by a comparison pulse of variable duration. The comparison stimulus was judged longer when its direction of motion differed from the standards, and when the same stimuli were presented to monkeys (albeit while the animals performed a different task), neurophysiological recording from the middle temporal area of the visual cortex (MT/V5) revealed that the firing rate and response-duration of these neurons was greater for the oddballs than the repeats.…”

Perceived Duration Increases with Contrast, but Only a Little

“…This difficulty comes from considering our results in the context of a recent study looking at repetition suppression and the oddball effect (Sadeghi et al, 2011). Recall firstly, that the oddball effect is the expansion of apparent duration of a novel stimulus presented within a train of repeated stimuli; and secondly, that repeated presentation of a stimulus suppresses the neural response associated with that stimulus (Li et al, 1993; Grill-Spector et al, 2006).…”

“…Sadeghi et al's (2011) study is particularly interesting because they look at the oddball effect using both human psychophysics and macaque electrophysiology. The stimulus they used, a random dot kinematogram, is a standard stimulus for driving neurons in motion area MT.…”

“…In order to match the previous set of stimuli (all 200 ms), the duration of the oddball had to be reduced to ~160 ms, whereas the duration of the repeat had to be increased to ~310 ms. For purpose of comparison, we can quantify the magnitude of this effect by taking the difference and dividing by the mean; which gives an effect magnitude of ~64%. Note that these figures, and those given below, are carefully estimated from Figures 1, 2 of Sadeghi et al (2011). …”

Ilusões temporais: Paradigma experimental

“…Designados de modelos de "dependência-de-estado" devido ao facto de ancorar nas mudanças de estado das redes neuronais durante a apresentação de um estímulo; sendo essa sucessão de padrões únicos de activação uma forma de codificar o próprio tempo. Eagleman e colaboradores (Eagleman, 2008;Eagleman & Pariyadath, 2009;Pariyadath & Eagleman, 2007;Sadeghi, Pariyadath, Apte, Eagleman, & Cook, 2011) adicionaram poder explicativo (de várias ilusões temporais) a estes modelos sugerindo que a duração subjectiva também depende, da eficiência da codificação neural 17 . Por outras palavras, quanto maior for a amplitude da resposta neural (ou energia despendida) promovida pelo estímulo, durações mais longas serão percebidas.…”