Remembering Forward: Neural Correlates of Memory and Prediction in Human Motor Adaptation

We used functional MR imaging (FMRI), a robotic manipulandum and systems identification techniques to examine neural correlates of predictive compensation for spring-like loads during goal-directed wrist movements in neurologically-intact humans. Although load changed unpredictably from one trial to the next, subjects nevertheless used sensorimotor memories from recent movements to predict and compensate upcoming loads. Prediction enabled subjects to adapt performance so that the task was accomplished with minimum effort. Population analyses of functional images revealed a distributed, bilateral network of cortical and subcortical activity supporting predictive load compensation during visual target capture. Cortical regions – including prefrontal, parietal and hippocampal cortices – exhibited trial-by-trial fluctuations in BOLD signal consistent with the storage and recall of sensorimotor memories or “states” important for spatial working memory. Bilateral activations in associative regions of the striatum demonstrated temporal correlation with the magnitude of kinematic performance error (a signal that could drive reward-optimizing reinforcement learning and the prospective scaling of previously learned motor programs). BOLD signal correlations with load prediction were observed in the cerebellar cortex and red nuclei (consistent with the idea that these structures generate adaptive fusimotor signals facilitating cancelation of expected proprioceptive feedback, as required for conditional feedback adjustments to ongoing motor commands and feedback error learning). Analysis of single subject images revealed that predictive activity was at least as likely to be observed in more than one of these neural systems as in just one. We conclude therefore that motor adaptation is mediated by predictive compensations supported by multiple, distributed, cortical and subcortical structures

Frontal Brain Injury: Effects on Flexibility, Impulse Control, and Attention

Traumatic Brain Injury (TBI) is defined as an impact to the head, penetration of the skull, or rapid deceleration of the skull, resulting in an alteration of brain function or neurological deficit. Cognitive deficits are common following TBI and often go unresolved due to a lack of effective treatments. These deficits often perseverate into the chronic post injury phase, so the development of rehabilitative strategies is imperative. Behavioral flexibility, impulse control, and attention are a few cognitive processes that are commonly affected by TBI. The current research compares these processes between rats with and without a severe frontal brain injury (TBI vs. Sham). Behavioral flexibility was measured with the attentional set shifting task (AST) and probabilistic reversal learning (PbR). Differential reinforcement of low rate behavior (DRL) was used to measure impulse control. Cues associated with correct responding were used compare attention between TBI and Sham rats. The cues also served as an environmental treatment for TBI related deficits. Behavioral flexibility, measured by AST performance, was not affected by TBI, however TBI rats were impaired relative to Sham rats on PbR. Sham rats performed better on DRL when compared to TBI rats, suggesting that impulse control was impaired by frontal TBI. The cue treatment improved performance for TBI and Sham rats on both PbR and DRL. On PbR, cues improved TBI performance to Sham levels. Cues also improved TBI performance on DRL, but not to Sham levels. These data suggest that frontal TBI impairs impulse control and behavioral flexibility. The improvement seen in TBI rats associated with the cue treatment suggest that attention may somewhat intact following a brain injury. In addition, the differential improvement between PbR and DRL performance suggests that TBI related deficits in impulse control may be more difficult to treat than deficits in behavioral flexibility

CNTRICS Final Task Selection: Long-term Memory

Long-term memory (LTM) is a multifactorial construct, composed of different stages of information processing and different cognitive operations that are mediated by distinct neural systems, some of which may be more responsible for the marked memory problems that limit the daily function of individuals with schizophrenia. From the outset of the CNTRICS initiative, this multidimensionality was appreciated, and an effort was made to identify the specific memory constructs and task paradigms that hold the most promise for immediate translational development. During the second CNTRICS meeting, the LTM group identified item encoding and retrieval and relational encoding and retrieval as key constructs. This article describes the process that the LTM group went through in the third and final CNTRICS meeting to select nominated tasks within the 2 LTM constructs and within a reinforcement learning construct that were judged most promising for immediate development. This discussion is followed by each nominating authors' description of their selected task paradigm, ending with some thoughts about future directions.Psycholog