Browsing by Subject "Lateral intraparietal"
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Item Decision-making in the primate brain : formation, location, and causal manipulation(2016-05) Katz, Leor Nadav; Huk, Alexander C.; Aldrich, Richard; Cormack, Lawrence K; Hayhoe, Mary; Priebe, Nicholas; Seidmann, EyalInteraction within the environment relies on the ability to accumulate sensory evidence in favor of a decision. Despite the paramount importance of decision-making to survival, the neural instantiations and computational principles governing the process have remained elusive. In this thesis I consider how sensory evidence is accumulated to guide decisions, and where in the primate brain this process takes place. I report the results of three main experiments. In the first, I test whether sensory evidence is accumulated differentially for motion in the frontoparallel plane (i.e. 2D motion; left/right) compared to motion through depth (i.e. 3D motion; towards/away). I show that integration of 3D motion is different than 2D and likely relies on a mechanism that is distinct. In the second experiment, I test an influential theory in cognitive neuroscience: that neurons in the monkey lateral intraparietal (LIP) cortex accumulate sensory information in favor of a decision communicated by an eye-movement. I found that despite strong correlations between LIP responses and decisions, reversible inactivation of neurons in LIP had no measurable impact on decision-making performance. More generally, I show that decision-related activity does not necessarily play a causal role in choices. In the final experiment, I test whether the process of making a decision stands to influence functions that are decision irrelevant. I found that causally manipulating the amount of sensory evidence available to human observers influenced decision-irrelevant oculomotor commands, suggesting that even during non- oculomotor decisions, oculomotor regions of the brain are recruited. Taken together, the experimental findings reported motivate new ideas about evidence accumulation and advance our understanding of the decision-making process in the primate brain.Item Statistical approaches for unraveling the neural code in the visual system(2015-08) Latimer, Kenneth William; Huk, Alexander C.; Pillow, Jonathan W.; Priebe, Nicholas J; Fiete, Ila R; Carvalho, Carlos MHere we consider the neural coding problem at two levels of the macaque visual system.First, we analyze single neurons recorded in the lateral intraparietal (LIP) cortex while a monkey performed a perceptual decision-making task. We relate the single-trial responses in LIP to stochastic decision-making processes with latent dynamical models. We compare models with latent spike rates governed by either continuous diffusion-to-bound dynamics or discrete ``stepping'' dynamics. In contrast to previous findings, roughly three-quarters of the choice-selective neurons we recorded are better described by the stepping model. Second, we introduce a biophysically inspired point process model that explicitly incorporates stimulus-induced changes in synaptic conductance in a dynamical model of neuronal membrane potential. We show that our model provides a tractable model of spike responses in macaque parasol retinal ganglion cells that is both more accurate and more interpretable than the popular generalized linear model. Most importantly, we show that we can accurately infer intracellular synaptic conductances from extracellularly recorded spike trains.