Spatial sensitivity of macaque inferior temporal neurons

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• Recent findings suggest dorsal visual stream areas and computational models raise questions about spatial coding in the ventral visual stream.
• Neurons in the anterior inferior temporal cortex (area TE) are at the end station of the ventral visual stream, making their spatial coding capabilities a key research question.

Purpose of the Study:

• To provide the first detailed, quantitative data on the spatial sensitivity of neurons in area TE of awake, fixating monkeys.
• To investigate the determinants of spatial sensitivity in TE neurons, including the role of spatial resolution and stimulus size.

Main Methods:

• Recorded spatial sensitivity of neurons in the anterior inferior temporal cortex (area TE) in awake, fixating monkeys.
• Analyzed receptive field (RF) size, optimal position, and RF profiles, fitting them with a two-dimensional Gaussian function.
• Tested the influence of low-pass filtered stimuli and varying stimulus sizes on spatial sensitivity.

Main Results:

• Observed significant variation in RF size (2.8–26 degrees) with a bias toward the foveal position.
• Most TE neurons exhibited a single region of high sensitivity with a smooth decline, well-described by Gaussian functions.
• Foveal preference and RF size were not solely due to lower spatial resolution at eccentric positions; stimulus size influenced RF broadening but not qualitative features.

Conclusions:

• TE neurons possess spatial sensitivity and can code for stimulus position within the central visual field.
• Spatial sensitivity is influenced by stimulus size but retains qualitative features, and size selectivity is largely position invariant.
• The findings contribute to understanding the functional role of the ventral visual stream in visual processing and spatial representation.