Systems neuroscience

Systems neuroscience is a subdiscipline of neuroscience which studies the neural circuit function, most commonly in awake, behaving intact organisms. This research area is concerned with how nerve cells behave when connected together to form neural networks that perform a common function: vision, for example, or voluntary movement. At this level of analysis, neuroscientists study how different neural circuits analyze sensory information, form perceptions of the external worlds, make decisions, and execute movements. Researchers concerned with systems neuroscience focus on the vast space that exists between molecular and cellular approaches to the brain and the study of high-level mental functions such as language, memory, and self-awareness (which are the purview of behavioral and cognitive neuroscience).

Major Topics
Systems neuroscience relies on precise, experimental recording methods such as single unit recording, calcium imaging and psychophysics analysis, which are used to pinpoint the reaction of the nervous system in response to external stimulus.

Vision
Systems level analysis in neuroscience has been most extensively carried out in the visual system, which began with work of Torsten Wiesel and David Hubel in characterizing, with single neuron electrophysiology, the properties simple cells in the primary visual cortex. Research has been intensive in characterizing the receptive field properties of various brain regions involved in visual processing.

Higher Executive Functions
Around 2006, Michael Shadlen and his lab used single-neuron recordings to examine how primates make decisions based on noisy evidence. They found that some neurons seem to tally up evidence in a manner much like one would work with log likelihood, and fire when a threshold is met. That is, they seem to perform Bayesian inference and trigger when the probability of a hidden state given the evidence is high.