Color Signals in Area MT of the Macaque Monkey

Abstract

The relationship between the neural processing of color and motion information has been a contentious issue in visual neuroscience. We examined this relationship directly by measuring neural responses to isoluminant S cone signals in extrastriate area MT of the macaque monkey. S cone stimuli produced robust, direction-selective responses at most recording sites, indicating that color signals are present in MT. While these responses were unequivocal, S cone contrast sensitivity was, on average, 1.0-1.3 log units lower than luminance contrast sensitivity. The presence of S cone responses and the relative sensitivity of MT neurons to S cone and luminance signals agree with functional magnetic resonance imaging (fMRI) measurements in human MT+. The results are consistent with the hypothesis that color signals in MT influence behavior in speed judgment tasks.

Microcircuitry for Two Types of Achromatic Ganglion Cell in Primate Fovea

“…Thus, the diffuse bipolar cells convey S-cone signals to at least three types of ganglion cell: parasol, garland, and the small, bistratified cell. Because the brisk-transient (parasol) pathway projects strongly to cortical area MT, it might be an important source for the strong S-cone signals in MT (Seidemann et al, 1999;Chatterjee and Callaway, 2002), although MT apparently gets some S-cone input via P cells (Nassi et al, 2006 Figure 4. B, Reconstructed dendritic trees (tangential view) from the cells in Figure 6 showing profiles of overlying cone terminals.…”

“…Third, are non-midget ganglion cells truly "achromatic," i.e., excited by all three cone types? Some studies report that parasol cells lack S-cone input (Dacey and Lee, 1994;Sun et al, 2006), whereas others find strong S-cone input to the M pathway and area MT (Seidemann et al, 1999;Chatterjee and Callaway, 2002). Finally, if the fovea contains different types of non-midget ganglion cell, as shown by Golgi staining (Polyak, 1941;Kolb et al, 1992) and retrograde labeling (Dacey et al, 2003), how does their circuitry differ?…”

Specializations for Chromatic and Temporal Signals in Human Visual Cortex

“…For example, one can compare spike-rate equivalent stimulus contrast values with BESC values. Notably, by using the stimulus-referred procedure, the neuroimaging, electrophysiological, and behavioral experiments can provide converging evidences for neural models (Dougherty et al, 1999;Seidemann et al, 1999;Wandell et al, 1999).…”

“…There is consistency between the motion selectivity of MT neurons and behavior (Britten et al, 1992). Conversely, MT receives weak S-cone signals (Seidemann et al, 1999;Wandell et al, 1999), and its receptive fields are relatively large (Albright and Desimone, 1987), making the circuitry poorly suited for detailed pattern vision or color. These observations support the theory that MT is specialized for motion processing.…”

Theories and methods in the scientific study of consciousness

“…It must however be noted that these functional distinctions are not absolute. In fact, MT-cells are still somewhat modulated by color signals (Seidemann, Poirson, Wandell, & Newsome, 1999), whereas the activity of V4-cells is also slightly influenced by visual motion (Ferrera, Rudolph, & Maunsell, 1994). The second class of functional elements in GNWT is formed by the workspace units that are characterized by their extensive connectivity with distant brain areas and mostly located in parietal, cingulate and prefrontal cortex.…”