Biomedical subjects

Penelope A Lewis

Publications and source records attributed to Penelope A Lewis.

5 recordsLinked to original sources

PubMed2004

Mediating stochastic switching of single molecules using chemical functionality.

We have studied oligo(phenylene-ethynylene)s inserted into amide-containing alkanethiol self-assembled monolayers using scanning tunneling microscopy to demonstrate switching based on chemical functionality of the environment of the inserted molecules. The molecules show stability in two conductance states: an ON and an OFF state. We demonstrate bias-dependent switching due to hydrogen bonding between the inserted oligo(phenylene-ethynylene) and the matrix molecules. In addition, the inserted molecules exhibit fewer switching events than previously reported for alkanethiol matrixes, which we attribute to the rigidity of the hydrogen-bonded matrix.

Journal Article↗

PubMed2003

Mood-dependent memory.

Have you ever noticed that when you are in a bad mood the whole world seems to be against you? More negative things seem to happen, and you even remember past episodes of your life in a more negative way than usual. Most of us have experienced this phenomenon, but few will have thought about how this mood might interact with our ability to remember. In a recent paper, Susanne Erk et al. shed light on a possible neural basis for this phenomena.

Journal Article↗

PubMed2003

Distinct systems for automatic and cognitively controlled time measurement: evidence from neuroimaging.

A recent review of neuroimaging data on time measurement argued that the brain activity seen in association with timing is not influenced by specific characteristics of the task performed. In contrast, we argue that careful analysis of this literature provides evidence for separate neural timing systems associated with opposing task characteristics. The 'automatic' system draws mainly upon motor circuits and the 'cognitively controlled' system depends upon prefrontal and parietal regions.

Animals↗

PubMed2002

Brain activity during non-automatic motor production of discrete multi-second intervals.

It has been suggested that the different patterns of brain activity observed during paced finger tapping and non-movement related timing tasks, with medial premotor cortex (supplementary motor cortex, pre and proper) and ipsilateral cerebellum dominating the former, and dorsolateral prefrontal cortex (DLPFC) the latter, might be related to differing motor demands. Since paced finger tapping often consists of automatic movement (requiring little overt attention), while non-motor timing is attentionally modulated, the difference could also be related to attentional processing. Here, we observed timing related activity in both medial premotor cortex and DLPFC, with non-timing related activity in other areas, including ipsilateral cerebellum, when subjects performed non-automatic motor timing. This result shows that, in time measurement, medial premotor activation is not specific to automatic movement, and DLPFC activity is not specific to non-motor tasks.

Adult↗

PubMed2002

Neuropsychology: time out of mind.

We have always known that some form of clock is needed to measure time. It now seems that a variety of different neural clocks are involved in determining our temporal perceptions, some specialised for shorter and some for longer durations.

Biological Clocks↗