Relationship between Size Summation Properties, Contrast Sensitivity and Response Latency in the Dorsomedial and Middle Temporal Areas of the Primate Extrastriate Cortex

Abstract

Analysis of the physiological properties of single neurons in visual cortex has demonstrated that both the extent of their receptive fields and the latency of their responses depend on stimulus contrast. Here, we explore the question of whether there are also systematic relationships between these response properties across different cells in a neuronal population. Single unit recordings were obtained from the middle temporal (MT) and dorsomedial (DM) extrastriate areas of anaesthetized marmoset monkeys. For each cell, spatial integration properties (length and width summation, as well as the presence of end- and side-inhibition within 15° of the receptive field centre) were determined using gratings of optimal direction of motion and spatial and temporal frequencies, at 60% contrast. Following this, contrast sensitivity was assessed using gratings of near-optimal length and width. In both areas, we found a relationship between spatial integration and contrast sensitivity properties: cells that summated over smaller areas of the visual field, and cells that displayed response inhibition at larger stimulus sizes, tended to show higher contrast sensitivity. In a sample of MT neurons, we found that cells showing longer latency responses also tended to summate over larger expanses of visual space in comparison with neurons that had shorter latencies. In addition, longer-latency neurons also tended to show less obvious surround inhibition. Interestingly, all of these effects were stronger and more consistent with respect to the selectivity for stimulus width and strength of side-inhibition than for length selectivity and end-inhibition. The results are partially consistent with a hierarchical model whereby more extensive receptive fields require convergence of information from larger pools of “feedforward” afferent neurons to reach near-optimal responses. They also suggest that a common gain normalization mechanism within MT and DM is involved, the spatial extent of which is more evident along the cell’s preferred axis of motion.

Gender differences in metabolic syndrome components among the Korean 66-year-old population with metabolic syndrome

“…The prevalence of MetS has been increasing [4, 14] over the last decades; this increase has been attributed to an increased incidence of dyslipidemia and abdominal obesity in Korean adults [4, 14]. Among old adults, MetS prevalence has been reported to vary from 20 to 60 %, with higher prevalence in females than males in several studies [3, 5–7, 15]. However, limited information is available regarding gender differences in MetS characteristics and components among older Koreans.…”

Functional MRI of visual responses in the awake, behaving marmoset

“…Previous electrophysiology studies using anesthetized marmosets have provided detailed knowledge about the organization of the marmoset’s visual system (Cheong et al, 2013; Lui et al, 2013; McDonald et al, 2014; Rosa and Tweedale, 2005; Yu and Rosa, 2014). Our study shows that fMRI experiments in the behaving animal can be used to complement electrophysiological studies.…”

“…Unlike macaques or humans, the cerebral cortex of the marmoset is lissencephalic, lacking the complex folding of sulci and gyri. Yet in spite of its superficial resemblance to the rat’s brain, the functional organization of the marmoset brain is that of a primate, with specializations in the eye and brain that closely resemble those found in macaques and humans (Cheong et al, 2013; Lui et al, 2013; McDonald et al, 2014; Mitchell and Leopold, 2015; Rosa and Tweedale, 2005; Yu and Rosa, 2014). …”

The marmoset monkey as a model for visual neuroscience

“…The electrophysiological responses of other visual areas in the marmoset have been studied in detail and generally resemble those of the macaque, including V2 (Rosa et al, 1997; Lui et al, 2005; Roe et al, 2005; Barraclough et al, 2006; Federer et al, 2009), DM (Rosa and Schmid, 1995; Lui et al, 2006; Lui et al, 2013), V3 (Rosa and Tweedale, 2000) and MT (Rosa and Elston, 1998; Solomon et al, 2011; Lui et al, 2007a; Lui et al, 2007b; Lui et al, 2012; Lui et al, 2013; McDonald et al, 2014; Solomon et al, 2014). …”