The advent of cranial implants revolutionized primate neurophysiological research because they allow researchers to stably record neural activity from monkeys during active behavior. Cranial implants have improved over the years since their introduction, but chronic implants still increase the risk for medical complications including bacterial contamination and resultant infection, chronic inflammation, bone and tissue loss and complications related to the use of dental acrylic. These complications can lead to implant failure and early termination of study protocols. In an effort to reduce complications, we describe several refinements that have helped us improve cranial implants and the wellbeing of implanted primates.

Humans and non-human animals parse the auditory scene into distinct auditory objects or "streams" by grouping together stimuli with common features and segregating those with different features. This process is commonly called "auditory scene analysis". Although previous studies have identified neural mechanisms in the primary (core) auditory cortex that may underlie auditory-stream segregation, we do not have a good understanding of the contribution of cortical regions outside of the core auditory cortex to stream segregation nor do we understand the laminar specificity of these contributions. To examine these issues, we recorded translaminar multiunit activity (MUA) from the core and belt auditory cortex in macaque monkeys while they participated in an auditory streaming task designed to provide an objective measure of auditory-stream segregation. We found that MUA encoded both the stimulus variables and the monkey's behavioral choices related to our streaming task. Overall, core MUA was modulated more by the stimulus variables and the monkey's choices than belt MUA. However, whereas neural correlates of these variables were uniformly distributed in the core auditory cortex, stimulus- and choice-related information was predominantly represented in the superficial and deep layers of belt, respectively. These findings support a differential representation of stimulus- and choice-related variables related to auditory scene analysis along the primate auditory cortical pathway.

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