Archive for the ‘Neuroscience and consciousness’ Category

P3b signal

Posted by

There appears no reason to reconsider the main drift of the distinctions between unconscious processing and conscious processing that has emerged in recent neuroscience, solely in the light of Silverstein and Snodgrass’s findings relative to the P3b signal. The P3b signal was formerly known as the P300 signal, but this latter is now seen as having two sub-components; the first of these, the P3a signal is mainly involved with directing attention, while P3b is involved with responding to more unusual stimuli, as opposed to routine stimuli. The signal is often correlated with conscious process of information in frontal brain regions. However, Silverstein and Snodgrass showed that it could also be stimulated by signals that were too short, or were masked so that they could not enter consciousness, but could nevertheless effect unconscious processing.

Altered states of consciousness

Posted by

It is argued that altered states, which can result from a range of cause including near-death-experience (NDE), meditation or psychedelic drugs, can be directly causal of durable personality changes. Further to this, recent experimentation suggests that some altered states can deactivate brain regions responsible both for the sense of self, and for constraining ‘mystical’ type experiences in other brain regions. Thus contrary to any suggestion that the self is some type of ‘mystical illusion’ it may in fact be part of a system that constrains ‘mystical’ experience during normal brain processing.

Opioid receptors

Posted by

A sub-population of the striatal direct-pathway neurons, known for being connected to voluntary movement, can be the basis of opiate-reward driven activities. The brain’s opioid system is basic to the reward value of stimuli and consequent behaviours. Opioid receptors bind to the brain’s opioid peptides such as enkephalin, β-endorphin, or dynorphin. μ-opioid receptors act to suppress the neuronal activity of neurons that otherwise…

Neural choices

Posted by

The brain is viewed as having two systems for making decisions. The first approach is to value actions according to the rewards they have generated in the past. A second or model-based approach uses more flexible evaluation of new or changing options, or works on generalisation from known

Ventromedial prefrontal

Posted by

This study shows that human decision-makers adapt their level of persistence in waiting for rewards to the environment in which the decision is being made. Neural signalling in the ventromedial prefrontal, an area involved with evaluation, could evolve differently for identical time delays, if there is a difference in the environment. The neural valuation system is here seen as including the ventromedial prefrontal (VMPFC), the ventral striatum (VS) and the posterior cingulate cortex

Sharp waves and memories

Posted by

The consolidation of memories depends on the hippocampus. The hipppocamus generates ripple activity, which is a sharp wave oscillation at 100-300 Hz, mainly within the CA1 region of the hippocampus. Sharp-wave associated field oscillations of the hippocampus, referred to as ripples, are thought to be involved in the consolidation of memories. The median raphe region

Observer’s choices

Posted by

The choices of other people are argued to increase the value of such choices for individuals. The related neural processing is encoded in the ventromedial prefrontal cortex, and the signals are predictive of conformity with other people’s preferences.

Agency and reward

Posted by

This paper can be taken as suggesting that a sense of agency is part of the reward system, encouraging repetition or non-repetition of particular actions or behaviours.

Ventromedial and confidence

Posted by

The ventromedial prefrontal cortex is the brain region most associated with ratings of the relative value of stimuli. Subjects are seen as assigning subjective values to the potential outcomes of possible actions leading to valuable results.

Libet v. recent neuroscience

Posted by

A source of despair in consciousness studies is the way in which popular science writers continue to plough ahead making pronouncements that are flatly contradicted by the neuroscientific data of recent years. In particular, consciousness students might be forgiven for screaming every time Libet’s veteran 1980s experiment is trundled out. Halligan and Oakley writing in a recent issue of ‘New Scientist’ go down this predictable route. The brain prepares for actions such as reaching out prior to awareness of the intention to reach.