The hypothalamus controls all homeostatic mechanisms. We study how the suprachiasmatic nucleus ("the biological clock") imposes a daily rhythm on other hypothalamic nuclei. Information is coded by the intervals between the spikes and we try to decode the patterns of spike activity. We use electrophysiological methods measuring activity by analysis of the intervals between spikes (Bhumbra and Dyball, J Physiol, 555, 281-296; Bhumbra et al J Physiol, 563, 292-307).
The statistical entropy of the probability distribution of the log inter-spike intervals quantifies their variability and the mutual information between adjacent log inter-spike intervals measures the extent of the occurrence of spike motifs. By musical analogy, frequency provides the key of the scale, the log interval entropy quantifies the timbre of the notes played on a particular musical instrument, and the mutual information quantifies the ordering of notes (the tune). Frequency, entropy, and mutual information each convey different information and can vary independently; one cannot be inferred simply from another. A tune sounds different when played on a different musical instrument but may be readily recognised regardless of the key in which it is played.
Dr GS Bhumbra, Univerity College London
Dr H Yamashita, Univerity of Occupational and Environmental Health, Kyushu Japan
Dr Claire Smith, Brighton & Sussex Medical School
Bhumbra GS, Dyball REJ, (2010), Reading between the spikes of the hypothalamic neural code, 22 1239-1250
Pallier PN , Maywood ES , Zheng Z, Chesham JE, Inyushkin AN, Dyball R, Hastings MH, Morton AJ, (2007), Pharmacological imposition of sleep slows cognitive decline and reverses dysregulation of circadian gene expression in a transgenic mouse model of Huntington's disease, Journal of Neuroscience, 27, 7869-7878
Bhumbra GS, Inyushkin AN, Saeb-Parsy K , Hon A, Dyball REJ, (2005), Rhythmic changes in spike coding in the rat suprachiasmatic nucleus, J Physiol, 563, 292 – 307
Bhumbra GS, Dyball REJ, (2004), Measuring Spike Coding in the Supraoptic Nucleus, J Physiol, 555, 281 - 296