(1) Cognitive Neuroscience of Exercise

(2) Neural Basis of Altered States of Consciousness

Actually, the THT started life as a general theory of altered states of consciousness (ASC). It occurred to me, on a cold February morning in New York City, of all places, that the hallmark of all altered ASC is the subtle modification of cognitive functions – working memory, sense of time, executive attention, sense of self, sense of willed action, etc – that are typically ascribed to the prefrontal cortex. It took me a few years to work out the details before I could publish the central idea I had that day; that is, the common neural mechanism that explains much of the phenomenology of ASC is the transient downregulation of prefrontal areas ( Dietrich, 2003).

Modern neuroscience conceptualizes mental function as hierarchically ordered. Evolutionary pressures forced the development of ever more integrative neural structures able to process increasingly complex information. This, in turn, led to increased cognitive flexibility. The cerebral cortex – the prefrontal cortex, especially – sits at the top of this hierarchy, representing the neural basis of higher cognitive functions. The THT, then, proposes the following. When the brain is taxed – by hypothermia, hypoxia, hypoglycemia, rhythmic dancing, sleep deprivation, drugs, to name a few possibilities – or its modus operanti is altered by either attentional processes – meditation, hypnosis, daydreaming, for instance – or by a brainstem controlled circadian rhythms – sleep, mostly – it starts switching off the lights on the top floors first, followed, in an onion-peeling principle of sorts, by the progressive inhibition of less fancy mental functions, all in order to continue running the operations that are critically needed at the time. It does not take much, apparently, for this process to kick in. Try sitting through a 5-hour Wagner opera. Executive attention is a very costly process that cannot be maintained for a long time and daydreaming is all but inevitable. In most ASC, prefrontal downregulation is as far as this goes – hence the name of the theory – but as such a situation continues – in deep meditation, to take one example – the brain is forced to go ever deeper into safe mode. The THT simply suggests, then, that this decline progresses from brain areas supporting the highest cognitive functions, down the functional hierarchy, one phenomenological subtraction at a time, to brain areas supporting the most basic ones. So the prefrontal cortex, being the most zenithal higher-order structure, is the first region whose computations are no longer supported sufficiently to reach muscles or consciousness. A person in an ASC, then, simply functions on the highest layer of consciousness that is left, making ASC not higher states of consciousness, as is often presumptuously thought, but a host of lower ones. Although the induction method starting this layer-peeling process is different for each ASC, with each twisting the content of consciousness in a unique way, the resulting phenomenology – sense of timelessness, drifting attention, being in the here and now, feeling of unity with the forces of nature, decreased awareness of surroundings, etc – is always consistent with a state of frontal hypofunction. I published various accounts of this theory ( Dietrich, 2003; Dietrich, 2004b) and made it also a central organizing theme for several chapters in my book Introduction to Consciousness ( Dietrich, 2007a).

My current interests in this area lie in (1) Cultural Anthropology: studying the collective rituals and ceremonies – think voodoo dancing, shamanism, or whirling dervishes here – that different cultures have invented to alter consciousness and (2) Cognitive Neuroscience: understanding in greater detail the neurocognitive changes that take place during ASC.

(3) Neurocognitive Mechanisms of Creativity and Flow