Sensory perception requires the extraction of useful information amid a noisy and constantly changing external environment. Understanding how the brain performs this impressive feat is one of the most important questions in neuroscience. However, the majority of laboratory experiments used to study neural coding use isolated stimuli and presume that the brain is a static, unchanging system. It has long been held that the process of adjusting to a changing environment - adaptation - affects the fundamental properties of the resulting cortical activity. Indeed, recent work from our own laboratory demonstrated a fundamental shift in the circuit's coding properties as a result of adaptation, shifting the cortex in a way that appears to make it better at discriminating between stimuli, but at the expense of its ability to detect weaker inputs. However, the precise link between the observed shifts in neural coding and the resulting behavioral manifestations remains as an important open question. In the work proposed here, the effect of adaptation to ongoing stimuli will be tested in awake rats performing whisker mediated detection and discrimination tasks. In parallel, anesthetized animals receiving the same stimuli will undergo voltage sensitive dye (VSD) imaging of cortex to provide an estimate of how the spatiotemporal evolution of sensory evidence is ultimately used to form a decision, as well as how this process is affected by adaptation. The results of this work could lead to multiple possible clinical applications. It has been shown that adaptation fails to alter discriminability of tactile inputs in autistic individuals, a finding that appears related to abnormalities in the cortical circuitry. Better understanding of the cortical effects of adaptation, and the related behavioral manifestations, could therefore lead to useful diagnostic tools for autism and related pathologies. In addition, sensory prostheses, from cochlear to retinal to thalamic and cortical implants, revolve around the ability to provide useful surrogate signals to sensory pathways. However, the effect of adaptation is lost without ongoing peripheral inputs. A more complete understanding of sensory adaptation and its effect on the resulting percept is therefore absolutely critical for the clinical success of engineered interfaces.
The purpose of this study is to better understand the process by which the brain integrates sensory information, allowing important stimuli to be extracted and identified amidst a noisy external environment. A more complete understanding of the this process could prove useful in understanding pathologies such as autism, which are caused by abnormalities in cortical circuitry that also appear to result in changes in basic sensory processing. This project also has direct relevance to the field of neural prosthetics, which seeks to replace lost sensory and motor function through direct interfacing with the nervous system.
|Ollerenshaw, Douglas R; Zheng, He J V; Millard, Daniel C et al. (2014) The adaptive trade-off between detection and discrimination in cortical representations and behavior. Neuron 81:1152-64|