Sensitivity of neurons in the middle temporal area of marmoset monkeys to random dot motion

Abstract

Neurons in the middle temporal area (MT) of the primate cerebral cortex respond to moving visual stimuli. The sensitivity of MT neurons to motion signals can be characterized by using random-dot stimuli, in which the strength of the motion signal is manipulated by adding different levels of noise (elements that move in random directions). In macaques, this has allowed the calculation of "neurometric" thresholds. We characterized the responses of MT neurons in sufentanil/nitrous oxide-anesthetized marmoset monkeys, a species that has attracted considerable recent interest as an animal model for vision research. We found that MT neurons show a wide range of neurometric thresholds and that the responses of the most sensitive neurons could account for the behavioral performance of macaques and humans. We also investigated factors that contributed to the wide range of observed thresholds. The difference in firing rate between responses to motion in the preferred and null directions was the most effective predictor of neurometric threshold, whereas the direction tuning bandwidth had no correlation with the threshold. We also showed that it is possible to obtain reliable estimates of neurometric thresholds using stimuli that were not highly optimized for each neuron, as is often necessary when recording from large populations of neurons with different receptive field concurrently, as was the case in this study. These results demonstrate that marmoset MT shows an essential physiological similarity to macaque MT and suggest that its neurons are capable of representing motion signals that allow for comparable motion-in-noise judgments. We report the activity of neurons in marmoset MT in response to random-dot motion stimuli of varying coherence. The information carried by individual MT neurons was comparable to that of the macaque, and the maximum firing rates were a strong predictor of sensitivity. Our study provides key information regarding the neural basis of motion perception in the marmoset, a small primate species that is becoming increasingly popular as an experimental model.

Auditory and Visual Motion Processing and Integration in the Primate Cerebral Cortex

“…However, the visual system goes one step further, with direction of motion being explicitly represented at the level of the single cell. Specifically, the spiking (action potential) responses of neurons are tuned to the direction of moving stimuli, meaning that they are more active in response to a specific direction of motion compared to other directions (Dubner and Zeki, 1971 ; Baker et al, 1981 ; Maunsell and Van Essen, 1983a ; Albright, 1984 ; Desimone and Ungerleider, 1986 ; Saito et al, 1986 ; Tanaka and Saito, 1989 ; Chaplin et al, 2017 ). Thus, direction selective neurons in the visual system can encode the direction of motion within their receptive fields.…”

“… Encoding of direction of motion in the visual and auditory systems. (A) A typical visual direction tuning curve from a neuron in the marmoset visual cortex (area MT) in response to a moving dot stimulus (data from Chaplin et al, 2017 ). The vertical line indicates the preferred direction of motion, and the inset shows the mean spiking responses (with the spontaneous rate subtracted) in polar plot form, showing clear direction selectivity.…”

Auditory motion does not modulate spiking activity in the middle temporal and medial superior temporal visual areas

“…We also presented an 8 ms full screen flash stimulus at 1 Hz (100 repeats) to test for visually evoked potentials. Robust direction selective spiking responses have been demonstrated for MT neurons in responses to these stimuli in the same preparation (Chaplin et al., ).…”

Circuit Mechanisms Governing Local vs. Global Motion Processing in Mouse Visual Cortex

“…Global motion computations have been studied in a variety of animal species from flies (Saleem et al, 2012 ) to humans (Adelson and Movshon, 1982 ). In particular, non-human primates have been extensively used as a model (Movshon et al, 1985 ; Newsome and Paré, 1988 ; Britten et al, 1992 ; Tinsley et al, 2003 ; Smith et al, 2005 ; Majaj et al, 2007 ; Hedges et al, 2011 ; Solomon et al, 2011 ; Kumbhani et al, 2015 ; Chaplin et al, 2017 ), yielding seminal insights. Only now, are mice being investigated (Juavinett and Callaway, 2015 ; Muir et al, 2015 ; Palagina et al, 2017 ).…”