Neural activities of monkey primary visual cortex: Contextual modulation and roles for initiation of saccadic eye movements

Abstract

In central visual system, primary visual cortex (V1) has been widely studied for visual information processes (Nassi & Callaway, 2009). One of the important issues in the processes within V1 is that the neural activities are highly context-dependent. In fact, we perceive and recognize one thing differently depending on the backgrounds of the scene itself or the level of attention on the object (Baluch & Itti, 2011

Todorovi?, 2010). Upon the issue, one big question remains

how would neurons in V1 deal with context dependency? It sounds simple, but investigating such processes comes along with a complexity and concerns in between internally ongoing states of physical system and externally stimulating assets of information. In order to answer parts of the big question above, I have done three independent studies with a specific question for each study regarding dynamics of V1 activity starting from low-level to high-level context dependent processes. Those questions include

1) How V1 activities are modulated between stimuli that are separated in space and time domains and what is the underlying mechanism of the modulation? 2) As being a brain region where given visual information is primarily reached, would the activity modulation in V1 show as much change along the dynamics in behavioral outcome? 3) Although primarily sensory, how would high-level context, especially expecting the time of upcoming stimulus modulate V1 activities? Throughout the studies in this thesis, it involved intensive analysis and interpretation from the results using two different signals, which are spike activity and local field potential (LFP). The signals may reflect different cortical processes, yet, may compensate to one another and provide essential evidence in information extraction (Quiroga & Panzeri, 2009). Other than those questions literally asked about V1 processes on contextual dependency and dynamic interaction, investigating the relationship between two different neural signals was another issue, which eventually showed complimentary effects of signal prediction from one another and showed some evidence in neural oscillations from LFP may indicate significance of its role in sensory selection (Schroeder & Lakatos, 2009). Purposely, those pieces of evidence in each study would provide important insights in neural mechanisms for various modulatory effects in visual processing and its relation to behavior as referred by saccadic eye movement.