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D Willingham

Publications and source records attributed to D Willingham.

7 recordsLinked to original sources
PubMed2005

Neural correlates of encoding and expression in implicit sequence learning.

In the domain of motor learning it has been difficult to separate the neural substrate of encoding from that of change in performance. Consequently, it has not been clear whether motor effector areas participate in learning or merely modulate changes in performance. Here, using a variant of the serial reaction time task that dissociated these two factors, we report that encoding during procedural motor learning does engage cortical motor areas and can be characterized by distinct early and late encoding phases. The highest correlation between activation and subsequent changes in motor performance was seen in the motor cortex during early encoding, and in the basal ganglia during the late encoding phase. Our results show that rapid encoding during procedural motor learning involves several distinct processes, and is represented primarily within motor system structures.

Adult↗
PubMed2002

Cerebellum activation associated with performance change but not motor learning.

The issue of whether the cerebellum contributes to motor skill learning is controversial, principally because of the difficulty of separating the effects of motor learning from changes in performance. We performed a functional magnetic resonance imaging investigation during an implicit, motor sequence-learning task that was designed to separate these two processes. During the sequence-encoding phase, human participants performed a concurrent distractor task that served to suppress the performance changes associated with learning. Upon removal of the distractor, participants showed evidence of having learned. No cerebellar activation was associated with the learning phase, despite extensive involvement of other cortical and subcortical regions. There was, however, significant cerebellar activation during the expression of learning; thus, the cerebellum does not contribute to learning of the motor skill itself but is engaged primarily in the modification of performance.

Brain↗
PubMed1999

Two novel human RAB genes with near identical sequence each map to a telomere-associated region: the subtelomeric region of 22q13.3 and the ancestral telomere band 2q13.

Two closely related genes have been identified at 2q13 and 22q13.3. These genes show similarity to members of the RAB family of small GTPases. RABL2A and RABL2B differ by three conservative amino acid changes over a total of 228 residues. Both are expressed in all tissues tested. Northern analysis showed that a 2.5-kb transcript is expressed in all tissues tested while a 1.4-kb transcript is specifically expressed only in muscle. The size difference between these two transcripts is the result of differential splicing of an intron within the 3' UTR. RABL2B is located within the subtelomeric region of 22q13.3. RABL2A maps to 2q13, the site of an ancestral telomere fusion event, suggesting that it also may be a subtelomeric gene.

Alternative Splicing↗
PubMed1997

Sequence comparison of human and yeast telomeres identifies structurally distinct subtelomeric domains.

We have sequenced and compared DNA from the ends of three human chromosomes: 4p, 16p and 22q. In all cases the pro-terminal regions are subdivided by degenerate (TTAGGG)n repeats into distal and proximal sub-domains with entirely different patterns of homology to other chromosome ends. The distal regions contain numerous, short (<2 kb) segments of interrupted homology to many other human telomeric regions. The proximal regions show much longer (approximately 10-40 kb) uninterrupted homology to a few chromosome ends. A comparison of all yeast subtelomeric regions indicates that they too are subdivided by degenerate TTAGGG repeats into distal and proximal sub-domains with similarly different patterns of identity to other non-homologous chromosome ends. Sequence comparisons indicate that the distal and proximal sub-domains do not interact with each other and that they interact quite differently with the corresponding regions on other, non-homologous, chromosomes. These findings suggest that the degenerate TTAGGG repeats identify a previously unrecognized, evolutionarily conserved boundary between remarkably different subtelomeric domains.

Base Sequence↗
PubMed1989

Explicit and implicit remembering: when is learning preserved in amnesia?

Amnesic patients can learn and retain a variety of skills. To investigate what distinguishes tasks that are within the learning abilities of amnesic patients from those that are not, we administered two tests to individuals with Korsakoff's syndrome and two control groups. One was a visual reaction time task with an embedded repeating sequence of stimulus positions. Response times of Korsakoff patients indicated that they learned this sequence and retained it normally for a week. The second task was a tactual stylus maze in which all blind alleys were blocked. Korsakoff patients were impaired in learning this maze, as assessed by the time required to trace it. Differences between the two tasks are outlined and the implications of these differences are discussed.

Adult↗