Thursday, April 19, 2012

Unresponsiveness and Unconsciousness.

It is conceptually uneasy to discriminate the two. It seems to me that some sort of Bohr's correspondence principle is becoming necessary in cognitive neuroscience. It's what we see with imaging technique really corresponding to the cognitive state we identify with our senses? In any way, remarkable paper (cool title too). 

Unresponsiveness ≠ Unconsciousness.:
Anesthesiology. 2012 Feb 6;
Authors: Sanders RD, Tononi G, Laureys S, Sleigh J

Consciousness is a subjective experience. During both sleep and anesthesia, consciousness is common, evidenced by dreaming. A defining feature of dreaming is that, while conscious, we do not experience our environment; we are disconnected. Besides inducing behavioral unresponsiveness, a key goal of anesthesia is to prevent the experience of surgery (connected consciousness), by inducing either unconsciousness or disconnection of consciousness from the environment. Review of the isolated forearm technique demonstrates that consciousness, connectedness, and responsiveness uncouple during anesthesia; in clinical conditions, a median 37% of patients demonstrate connected consciousness. We describe potential neurobiological constructs that can explain this phenomenon: during light anesthesia the subcortical mechanisms subserving spontaneous behavioral responsiveness are disabled but information integration within the corticothalamic network continues to produce consciousness, and unperturbed norepinephrinergic signaling maintains connectedness. These concepts emphasize the need for developing anesthetic regimens and depth of anesthesia monitors that specifically target mechanisms of consciousness, connectedness, and responsiveness.

PMID: 22314293 [PubMed - as supplied by publisher]

Monday, April 16, 2012

Chronobiology going wild

This is IMHO a great paper! I have been so fascinated by the findings that I can't help asking myself several questions about how careful must a lab setup be set. And what about human study? Will this paper put human lab out of business? For now, this seems like some sort of Heisenberg uncertainty principle applied to biology: to do the correct measurement, you need to use a lab setup, but in the lab setup, your measure will result different. Lots to think about.

Unexpected features of Drosophila circadian behavioural rhythms under natural conditions:

Nature advance online publication 04 April 2012. doi:10.1038/nature10991

Authors: Stefano Vanin, Supriya Bhutani, Stefano Montelli, Pamela Menegazzi, Edward W. Green, Mirko Pegoraro, Federica Sandrelli, Rodolfo Costa & Charalambos P. Kyriacou

Circadian clocks have evolved to synchronize physiology, metabolism and behaviour to the 24-h geophysical cycles of the Earth. Drosophila melanogaster’s rhythmic locomotor behaviour provides the main phenotype for the identification of higher eukaryotic clock genes. Under laboratory light–dark cycles, flies show enhanced activity before lights on and off signals, and these anticipatory responses have defined the neuronal sites of the corresponding morning (M) and evening (E) oscillators. However, the natural environment provides much richer cycling environmental stimuli than the laboratory, so we sought to examine fly locomotor rhythms in the wild. Here we show that several key laboratory-based assumptions about circadian behaviour are not supported by natural observations. These include the anticipation of light transitions, the midday ‘siesta’, the fly’s crepuscular activity, its nocturnal behaviour under moonlight, and the dominance of light stimuli over temperature. We also observe a third major locomotor component in addition to M and E, which we term ‘A’ (afternoon). Furthermore, we show that these natural rhythm phenotypes can be observed in the laboratory by using realistic temperature and light cycle simulations. Our results suggest that a comprehensive re-examination of circadian behaviour and its molecular readouts under simulated natural conditions will provide a more authentic interpretation of the adaptive significance of this important rhythmic phenotype. Such studies should also help to clarify the underlying molecular and neuroanatomical substrates of the clock under natural protocols.