Archive for the ‘Neuroscience’ Category

P3b signal

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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

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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.

Stimulus-specific adaptation

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This research relates to the ability of the auditory system to recognise sounds as the same word, even at widely different pitches and speeds, and also the greater sensitivity of hearing for unexpected as opposed to expected sounds. In the wild, the unexpected or infrequent sound might warn of the approach of a predator, in contrast to the more general background noises of nature.

Brain oscillations

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Humans can perform short-term actions while remaining aware of longer-term goals. Evidence suggests that prefrontal areas coordinate motor activity when such goals are being aimed at. The more that abstract rules are involved, the more there is a combination of theta (4-8 Hz) and high gamma (80-150 Hz) phase together with inter-regional information encoding in the frontal cortex.

Personal traits

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Humans can look beyond immediate positive and negative experiences, and can additionally encode behavioural traits. Both learning from reward and learning from traits involve processing in the ventral striatum. Learning about traits allows another person to be valued in contexts other than the immediate one, and this can be important in social decision-taking.

Opioid receptors

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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

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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

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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

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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

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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.