Our long-term goals are to understand how somatosensory information is processed dynamically during purposeful hand movements and how motor activity associated with those movements differs with changes in behavioral context. As direct extensions of previous work, we seek to understand when and under what behavioral circumstances sensory responsiveness and movement-related sensorimotor cortical activity are altered during behaviors involving use of partial task information and during decision-making. These experiments use controlled behaviors and systematically vary cues needed for successful outcomes.
Specific Aim #1 is to determine if, when explicit information about target location and/or timing of movement onset is present, sensory responses and movement-related activity of sensorimotor cortical neurons change significantly, and if so, to determine if responsiveness changes are consistent with predictions about sensory responsiveness during movement planning and execution. Using single-unit recording techniques and behaving animals, we will determine if modulation of sensorimotor cortical neuronal responsiveness and movement/activity correlations differ when movements can be planned using information about movement onset or target location, but not both in the same behavioral trial.
Specific Aim #2 is to determine if, during decision-making, prior success influences sensory responses and movement-related activity of sensorimotor cortical neurons and if so, to determine if responsiveness changes are altered most when decisions are reinforced or when they are countermanded. We will also determine how changes in sensory responsiveness and movement/activity correlations relate to the well- documented """"""""win-stay-loss-switch"""""""" decision-making behavior of animals in free-choice or instructed paradigms. All findings will be related to reward history to see how it influences behavior. In both sets of experiments, data will be analyzed to quantify firing rates and the fidelity with which cortical neurons represent peripheral sensory stimuli that are the same but have different meanings depending on behavioral context. Motor-related activity will be fitted to movement kinematics to determine differences as a function of behavior. Stroke involving sensorimotor cortices is common but often followed by good functional recovery. Recovery may be due to central nervous system reorganization. Reorganization is facilitated by movement therapy that mimics normal behavioral repertoires. What controls the expression of normal repertoire, however, is still poorly understood. By understanding how, where, and when somatosensory responsiveness and movement-related cortical activity are modified during planning and decision-making behaviors, deficits can be more readily assessed and localized, and retraining strategies more appropriately applied.
| Liu, Yu; Denton, John M; Nelson, Randall J (2008) Monkey primary somatosensory cortical activity during the early reaction time period differs with cues that guide movements. Exp Brain Res 187:349-58 |
| Liu, Yu; Denton, John M; Nelson, Randall J (2007) Neuronal activity in monkey primary somatosensory cortex is related to expectation of somatosensory and visual go-cues. Exp Brain Res 177:540-50 |
| Liu, Yu; Denton, John M; Frykberg, Brett P et al. (2006) Detecting neuronal activity changes using an interspike interval algorithm compared with using visual inspection. J Neurosci Methods 155:49-55 |
| Liu, Yu; Denton, John M; Nelson, Randall J (2005) Neuronal activity in primary motor cortex differs when monkeys perform somatosensory and visually guided wrist movements. Exp Brain Res 167:571-86 |
| Lebedev, M A; Nelson, R J (1999) Rhythmically firing neostriatal neurons in monkey: activity patterns during reaction-time hand movements. J Neurophysiol 82:1832-42 |
