Abstract
Attention leads eye movements producing perceptual enhancements at the saccade target immediately before saccades (Deubel and Schneider, 1996; Kowler et al, 1995; Rolfs and Carrasco, 2012). Pre-saccadic attention has been related to enhanced neural responses before saccades made into a neuron’s receptive field in macaque visual area V4 (Moore and Chang, 2009). Here, we examined pre-saccadic attention in the middle temporal area (MT) of the marmoset monkey and took advantage of their smooth cortical surface to measure neural effects as a function of laminar position. First, we find that current source density (CSD) methods provide estimates of the input layer in area MT based on an early latency sink. Next we examined pre-saccadic attention in a saccade foraging paradigm. In each trial, the marmoset made a saccade from a central fixation point to one of three equally eccentric stimuli (full coherence dot fields with motion sampled independently between apertures, each from 16 directions). We positioned stimuli such that one foraged location overlapped the receptive fields of neurons under study and examined how tuning functions for motion direction changed (i.e., additive and gain changes). We found that saccades towards the receptive field were associated with increases in gain that were predominantly in superficial layers while additive increases in rate were shared across all layers. We also examined the extracellular waveform shapes and found a bi-modal distribution of peak-to-trough durations (i.e., narrow and broad spiking categories). In particular, the gain increases among superficial layer neurons were specific to the broad spiking category. Broad spiking neurons in those layers should include projection cells that relay information to other cortical areas. This suggests that increases in sensitivity could be specific to cell classes that output sensory information to later stages of processing involved in decision making.