Circadian rhythms are endogenously generated by the suprachiasmatic nuclei (SCN) of the hypothalamus and are entrained to the 24 h day primarily by the light-dark cycle (the major environmental time cue) and, to a lesser extent, by non-photic time cues (e.g. social interaction, novel activity, exercise). Outputs from the SCN control the rhythmicity of many physiological and behavioural processes (e.g. hormone secretion, core body temperature, sleep, activity). Disorders of circadian system may have serious consequences. Shift-work and jet-lag are examples in which the endogenous circadian system is desynchronised from the external environment. Blind individuals are also likely to suffer from circadian rhythm disorders (abnormal sleep, hormonal and behavioural rhythms) as they lack the eye-mediated photic input to the SCN required to entrain endogenous rhythms to the light-dark cycle. In order to resynchronise disordered rhythms, treatment (e.g. light or exogenous melatonin) must be given at an appropriate time according to each individual's circadian system. It is not yet established how similar circadian period (t) is between individuals. An assessment of period, unaffected by the external environment, is required in order to evaluate how robust and repeatable the measurement of human circadian rhythms are. A recent publication by Harvard Medical School has proposed that t = 24.18 h in sighted subjects studied in a laboratory-based 'forced desynchrony' protocol whereas our field studies of blind people at the University of Surrey suggest a higher average (=24.5h). The forced desynchrony protocol tightly controls the subjects' exposure to external influences by maintaining them on a 28 hour sleep-wake schedule and keeping them in constant dim light (15 lux) for 30 days. As 28 hours is beyond the range of entrainment for human rhythms, the circadian system reverts to its endogenous periodicity. This is in contrast to the field studies of totally blind individuals where light cannot influence the subjects, no restrictions are placed on them and exposure to non-photic time cues is unrestricted. The variation in experimental techniques used in these studies has prevented a definitive consensus on the value of t. Whether the inconsistencies observed between the two approaches are due to differences in experimental technique, the use of sighted and blind subjects or exposure to photic and non-photic time cues is unknown. Thus, the overall aim of the project is to define the endogenous period (t) of the human circadian system and to examine the influence of non-photic time cues on rhythmicity. The proposed study will assess the circadian period of six totally blind subjects in the laboratory using the forced desynchrony protocol and will be compared to the period measured in field studies in the same individuals. By studying blind subjects, the potentially confounding influences of light are removed, allowing an assessment of the effects of an altered distribution of non-photic time cues between the two methods. The findings will be used to assess the stability and precision of the human circadian pacemaker and to evaluate the potential of a general model to treat circadian rhythm disorders.

It is being increasingly recognised that there is a need for the theoretical unification of knowledge from different disciplines in our quest for understanding the cognitive function and structure of the human brain. Current advances (genetic and behavioural) in our knowledge of specific language impairment in children and, more generally, the study of language in cognitive science makes this an ideal locus for such unification. There is a strong interdependence between genetic, linguistic, and behavioural understanding of SLI and related areas of cognitive and linguistic development, which determines current and future investigations. Thus, the recent genetic advances in the understanding of SLI, the broadening knowledge of the nature of SLI and related areas of cognitive science, makes this symposium-workshop very timely. Furthering understanding between the disciplines is likely to influence future investigations in their respective disciplines. Topics to be covered: Genes and cognitive science: Genetics advances in SLI Behavioural Genetics Syntactic rules in Babies - work integrating cognitive science, connectionism and biology Language and cognitive science Current advances in language acquisition: Phonological bootstrapping in babies Phonology and domain specificity and plasticity Word-learning in normally developing children Grammatical acquisition Current advances in SL1: Longitudinal linguistic and neurolinguistic (ERP) study of children at risk of SLI from birth (Leipzig/Potsdam study) Longitudinal twin study (UK) Heterogeneity and SLI subgroups - and the significance to genetic and behavioural studies Linguistic perspective on SL1 Cognitive and language disorders: Cognitive development - domain general viewpoint, William's syndrome Language and cognitive development, Autism Dyslexia and FMRI Developmental Psycholinguistics and cognitive science: Lexical representation Linguistic perspectives on sentence processing in children, William's syndrome ERP and FMRI syntactic and semantic sentence processing in children and adults Memory, language and cognitive neuroscience (ERP)