Synchronization Dynamics in Response to Plaid Stimuli in Monkey V1

Abstract

Gamma synchronization has generally been associated with grouping processes in the visual system. Here, we examine in monkey V1 whether gamma oscillations play a functional role in segmenting surfaces of plaid stimuli. Local field potentials (LFPs) and spiking activity were recorded simultaneously from multiple sites in the opercular and calcarine regions while the monkeys were presented with sequences of single and superimposed components of plaid stimuli. In accord with the previous studies, responses to the single components (gratings) exhibited strong and sustained gamma-band oscillations (30–65 Hz). The superposition of the second component, however, led to profound changes in the temporal structure of the responses, characterized by a drastic reduction of gamma oscillations in the spiking activity and systematic shifts to higher frequencies in the LFP (∼10% increase). Comparisons between cerebral hemispheres and across monkeys revealed robust subject-specific spectral signatures. A possible interpretation of our results may be that single gratings induce strong cooperative interactions among populations of cells that share similar response properties, whereas plaids lead to competition. Overall, our results suggest that the functional architecture of the cortex is a major determinant of the neuronal synchronization dynamics in V1.

Intersubject variability and induced gamma in the visual cortex: DCM with empirical Bayes and neural fields

“…In particular, the spatial structure of the visual stimulus has been shown to affect gamma band activity [Bauer et al, 1995; Gieselmann and Thiele, 2008; Lima et al, 2010]. In our earlier work [Perry et al, 2013], we tested the relationship between the gamma‐band response and the size of visual grating stimuli in humans using MEG.…”

Visual stimulus eccentricity affects human gamma peak frequency

“…Recently, Lima et al (2010) found a negative relation between stimulus eccentricity and gamma peak frequency. They recorded from two sites in V1 with receptive fields at eccentricities of 3 and 10 ° while the monkey was shown a single, moving grating that encompassed the receptive fields of both recording sites.…”

“…The decline in representation volume is roughly linear (Slotnick et al 2001), so if a given stimulus activates a cortical volume V when presented at the fovea, it will activate a cortical volume V/M, when placed in the periphery, with M describing the amount of cortical magnification at the fovea relative to this specific peripheral location. In this context, the moving grating stripes of the stimuli used by Lima et al (2010), will move faster across the cortical surface when presented peripheral, than when presented perifoveally. We will refer to this concept as "cortical velocity".…”

“…Gamma peak frequency shifts to higher frequency values for higher contrast, faster moving, and attended stimuli. In monkey V1, gamma peak frequency for a drifting grating is higher for a parafoveal as compared to an eccentric stimulus (Lima et al, 2010). This effect might be due to the cortical magnification factor: the higher cortical magnification for parafoveal stimuli increases the velocity with which the cortical representations of the moving grating stripes move across the cortical surface.…”

Significant reductions in human visual gamma frequency by the gaba reuptake inhibitor tiagabine revealed by robust peak frequency estimation

“…The peak frequency of visual gamma responses is modulated by properties of the visual stimulus such as size [Gieselmann and Thiele, 2008; Jia et al, 2013; Ray and Maunsell, 2011; van Pelt and Fries, 2013], contrast [Hadjipapas et al, 2015; Jia et al, 2013; Lowet et al, 2015; Perry et al, 2015; Ray and Maunsell, 2010; Roberts et al, 2013], motion [Friedman‐Hill, 2000; Muthukumaraswamy and Singh, 2013; Swettenham et al, 2009], motion velocity [Gray et al, 1990; Gray and Viana Di Prisco, 1997; Orekhova et al, 2015], eccentricity [van Pelt and Fries, 2013], noise masking [Jia et al, 2013], and cross‐orientation masking [Lima et al, 2010; Perry, 2015]. Across individuals, peak gamma frequency correlates with psychophysical performance in visual discrimination tasks [Dickinson et al, 2015; Edden et al, 2009].…”