Biology subjects

Templer, J. W.

Publications and source records attributed to Templer, J. W..

3 recordsLinked to original sources

bioRxiv2020

Distinct representations of finger movement and force in human motor and premotor cortices

The ability to grasp and manipulate objects requires controlling both finger movement kinematics and isometric force. Previous work suggests that these behavioral modes are controlled separately, but it is unknown whether the cerebral cortex represents them differently. Here, we investigated this question by recording high-density electrocorticography from the motor and premotor cortices of seven human subjects performing a sequential movement-force motor task. We decoded finger movement (0.7{+/-}0.3 fractional variance account for; FVAF) and force (0.7{+/-}0.2 FVAF) with high accuracy, yet found different spatial representations. We also found clear distinctions in electrocorticographic activity by using deep learning methods to uncover state-space representations, and by developing a new metric, the neural vector angle. Thus, state-space techniques can help to investigate broad cortical networks. Finally, we were able to classify the behavioral mode from neural signals with high accuracy (90{+/-}6%). Thus, finger movement and force have distinct representations in motor/premotor cortices. This will inform our understanding of the neural control of movement as well as the design of grasp brain-machine interfaces.

neuroscience↗

bioRxiv2019

Hippocampal theta coordinates memory processing during visual exploration

The hippocampus supports memory encoding and retrieval, with distinct phases of theta oscillations modulating the amplitude of gamma-band activity during each process. Encoding and retrieval operations dynamically interact over rapid timescales, especially when sensory information conflicts with memory. The ability to link hippocampal dynamics to specific memory-guided behaviors has been limited by experiments that lack the temporal resolution to segregate when encoding and retrieval occur. To resolve this issue, we simultaneously tracked eye movements and hippocampal field potentials while neurosurgical patients performed a spatial memory task. Novelty-driven fixations increased phase-locking to the theta rhythm, which predicted successful memory performance. Theta to gamma phase amplitude coupling increased during these viewing behaviors and predicted forgetting of conflicting memories. In contrast, theta phase-locking preceded fixations initiated by memory retrieval, indicating that the hippocampus coordinates memory-guided eye movements. These findings suggest that theta oscillations in the hippocampus support learning through two interleaved processes: strengthening the encoding of novel information and guiding exploration based on prior experience.

neuroscience↗

bioRxiv2017

Differential representation of articulatory gestures and phonemes in motor, premotor, and inferior frontal cortices

Speech is a critical form of human communication and is central to our daily lives. Yet, despite decades of study, an understanding of the fundamental neural control of speech production remains incomplete. Current theories model speech production as a hierarchy from sentences and phrases down to words, syllables, speech sounds (phonemes) and the movements of speech articulator muscles used to produce these sounds (articulatory gestures). Here, we investigate the cortical representation of articulatory gestures and phonemes in speech motor, premotor, and inferior frontal cortices. Our results indicate that primary motor and premotor areas represent gestures to a greater extent than phonemes, while inferior frontal cortex represents both gestures and phonemes. These findings suggest that the cortical control of speech production shares a common representation with that of other types of movement, such as arm and hand movements.

neuroscience↗