Neural Substrates of Response-based Sequence Learning using fMRI

Abstract

Abstract& Representation of sequential structure can occur with respect to the order of perceptual events or the order in which actions are linked. Neural correlates of sequence retrieval associated with the order of motor responses were identified in a variant of the serial reaction time task in which training occurred with a spatially incompatible mapping between stimuli and finger responses. After transfer to a spatially compatible version of the task, performance enhancements indicative of learning were only present in subjects required to make finger movements in the same order used during training. In contrast, a second group of subjects performed the compatible task using an identical sequence of stimuli (and different order of finger movements) as in training. They demonstrated no performance benefit, indicating that learning was response based. Analysis was restricted to subjects demonstrating low recall of the sequence structure to rule out effects of explicit awareness. The interaction of group (motor vs. perceptual transfer) with sequence retrieval (sequencing vs. rest) revealed significantly greater activation in the bilateral supplementary motor area, cingulate motor area, ventral premotor cortex, left caudate and inferior parietal lobule for subjects in the motor group (illustrating successful sequence retrieval at the response level). Retrieval of sequential responses occurs within mesial motor areas and related motor planning areas. &

Evidence for separate representations for action and location in implicit motor sequencing

“…Given that the implicit group learned both location and action sequences, it is surprising that the explicit-locations group did not demonstrate learning the sequence of actions. This result conflicts with previous research that has demonstrated that explicit knowledge does not interfere with implicit acquisition of sequences (Bischoff-Grethe, Goedert, Willingham, & Grafton, 2004;Mayr, 1996;Willingham & GoedertEschmann, 1999;Willingham, Salidis, & Gabrieli, 2002). Given these prior findings, we think it improbable that explicit knowledge of the stimulus sequence interfered with implicit acquisition of the action sequence.…”

“What” Becoming “Where”: Functional Magnetic Resonance Imaging Evidence for Pragmatic Relevance Driving Premotor Cortex

“…In some studies, dorsal PM has been reported to be specifically engaged in nonstandard mapping, referring to spatially incompatible mappings, in contrast to spatially compatible ones (Iacoboni et al, 1998;Bischoff-Grethe et al, 2004). Because spatial mapping is inherent to both compatible and incompatible mappings in these tasks, spatial mapping alone cannot account for stronger dorsal PM activation in incompatible mappings.…”

Evidence for a distributed hierarchy of action representation in the brain

“…Depending on training conditions, it is possible to demonstrate that participants are learning the perceptual ordering of stimuli in the task, the discrete motor responses in the task, or the outcome of the responses, that is, the distal goals or consequences of the action (Bapi, Doya, & Harner, 2000;Hazeltine, 2002). With SRT sequence learning there is typically increasing activity in supplementary motor area (SMA) or pre-supplementary motor area (pre-SMA) and the inferior parietal lobule (IPL) (Bapi, Miyapuram, Graydon, & Doya, 2006;Bischoff-Grethe, Goedert, Willingham, & Grafton, 2004;Grafton et al, 1995;Grafton, Hazeltine, & Ivry, 1998). At a single neuron level, coding for sequence order in a very small set of over-learned movements is observed in SMA in humans (Amador & Fried, 2004) and in monkeys within SMA, pre-SMA (Tanji, 1996;Tanji & Shima, 1994) and IPL as well as the motor cortex (Lu & Ashe, 2005) but not in regions associated with reaching (Batista & Andersen, 2001).…”