Spatial and temporal frequency selectivity of neurons in the middle temporal visual area of new world monkeys (Callithrix jacchus).

Publisher: Wiley-Blackwell Country of Publication: France NLM ID: 8918110 Publication Model: Print Cited Medium: Print ISSN: 0953-816X (Print) Linking ISSN: 0953816X NLM ISO Abbreviation: Eur J Neurosci Subsets: MEDLINE

Publication: : Oxford : Wiley-Blackwell
Original Publication: Oxford, UK : Published on behalf of the European Neuroscience Association by Oxford University Press, c1989-

Brain Mapping*; Action Potentials/*physiology ; Callithrix/*anatomy & histology ; Motion Perception/*physiology ; Neurons/*physiology ; Visual Cortex/*cytology; Animals ; Cell Count/methods ; Models, Neurological ; Photic Stimulation ; Visual Fields/physiology ; Visual Pathways/physiology

Information about the responses of neurons to the spatial and temporal frequencies of visual stimuli is important for understanding the types of computations being performed in different visual areas. We characterized the spatiotemporal selectivity of neurons in the middle temporal area (MT), which is deemed central for the processing of direction and speed of motion. Recordings obtained in marmoset monkeys using high-contrast sine-wave gratings as stimuli revealed that the majority of neurons had bandpass spatial and temporal frequency tuning, and that the selectivity for these parameters was largely separable. Only in about one-third of the cells was inseparable spatiotemporal tuning detected, this typically being in the form of an increase in the optimal temporal frequency as a function of increasing grating spatial frequency. However, most of these interactions were weak, and only 10% of neurons showed spatial frequency-invariant representation of speed. Cells with inseparable spatiotemporal tuning were most commonly found in the infragranular layers, raising the possibility that they form part of the feedback from MT to caudal visual areas. While spatial frequency tuning curves were approximately scale-invariant on a logarithmic scale, temporal frequency tuning curves covering different portions of the spectrum showed marked and systematic changes. Thus, MT neurons can be reasonably described as similarly built spatial frequency filters, each covering a different dynamic range. The small proportion of speed-tuned neurons, together with the laminar position of these units, are compatible with the idea that an explicit neural representation of speed emerges from computations performed in MT.

Date Created: 20070417 Date Completed: 20070626 Latest Revision: 20070416

20221213

10.1111/j.1460-9568.2007.05453.x

17432965