The term posterior cortical hot zone was coined by Christof Koch and colleagues to describe the part of the neocortex closely associated with the minimal neural substrate essential for conscious perception. [1] The posterior cortical hot zone includes sensory cortical areas in the parietal, temporal, and occipital lobes. It is the “sensory” cortex, much as the frontal cortex is the “action” cortex.
When parts of the posterior cortex are damaged, whole modalities of sensory experience disappear from both waking and dreaming. For example, individuals with a lesion in the Visual area V4 often do not perceive color and dream in black-and-white; those with a lesion in the Visual area V5/MT do not perceive motion and do not dream of motion; subjects with a lesion to fusiform gyrus are impaired in face perception and also do not dream of faces. [2] Compare that to lesions of the cerebellum or frontal cortex that have little effect on sensory experience.
The sensory component (shape, color, texture) of each object stored in memory is physically encoded by neurons of the posterior cortical hot zone in structures called neuronal ensembles (NEs), neuronal assemblies, [3] neural cliques, [4] or cognits. [5] When one recalls any object, the object-encoding neuronal ensemble (objectNE) in the posterior cortical hot zone activates into synchronous resonant activity that results in conscious perception of the object. The objectNE binding mechanism, based on the Hebbian principle “neurons that fire together, wire together,” came to be known as the Binding-by-Synchrony hypothesis. [6]
While the Hebbian principle explains how we perceive a familiar object, it does not explain the infinite number of novel objects that humans can imagine. To account for the limitless constructive imagination, it was proposed that synchronization of independent objectNEs is a general mechanism underlying any novel imaginary experience. [7] When the synchronization of independent objectNEs is driven from the front by the lateral prefrontal cortex, we refer to it as Prefrontal Synthesis; when the synchronization is driven from the back, we refer to it as dreaming or hallucination.
The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 (V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5.
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The claustrum is a thin sheet of neurons and supporting glial cells, that connects to the cerebral cortex and subcortical regions including the amygdala, hippocampus and thalamus of the brain. It is located between the insular cortex laterally and the putamen medially, encased by the extreme and external capsules respectively. Blood to the claustrum is supplied by the middle cerebral artery. It is considered to be the most densely connected structure in the brain, and thus hypothesized to allow for the integration of various cortical inputs such as vision, sound and touch, into one experience. Other hypotheses suggest that the claustrum plays a role in salience processing, to direct attention towards the most behaviorally relevant stimuli amongst the background noise. The claustrum is difficult to study given the limited number of individuals with claustral lesions and the poor resolution of neuroimaging.
In the philosophy of mind, neuroscience, and cognitive science, a mental image is an experience that, on most occasions, significantly resembles the experience of "perceiving" some object, event, or scene but occurs when the relevant object, event, or scene is not actually present to the senses. There are sometimes episodes, particularly on falling asleep and waking up, when the mental imagery may be dynamic, phantasmagoric, and involuntary in character, repeatedly presenting identifiable objects or actions, spilling over from waking events, or defying perception, presenting a kaleidoscopic field, in which no distinct object can be discerned. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined.
The consciousness and binding problem is the problem of how objects, background and abstract or emotional features are combined into a single experience.
The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to language switching. It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans, curving down and onto the medial surface, on the superior temporal plane, within the lateral sulcus and comprising parts of the transverse temporal gyri, and the superior temporal gyrus, including the planum polare and planum temporale.
Visual memory describes the relationship between perceptual processing and the encoding, storage and retrieval of the resulting neural representations. Visual memory occurs over a broad time range spanning from eye movements to years in order to visually navigate to a previously visited location. Visual memory is a form of memory which preserves some characteristics of our senses pertaining to visual experience. We are able to place in memory visual information which resembles objects, places, animals or people in a mental image. The experience of visual memory is also referred to as the mind's eye through which we can retrieve from our memory a mental image of original objects, places, animals or people. Visual memory is one of several cognitive systems, which are all interconnected parts that combine to form the human memory. Types of palinopsia, the persistence or recurrence of a visual image after the stimulus has been removed, is a dysfunction of visual memory.
A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 25 and 140 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.
In psycholinguistics, language processing refers to the way humans use words to communicate ideas and feelings, and how such communications are processed and understood. Language processing is considered to be a uniquely human ability that is not produced with the same grammatical understanding or systematicity in even human's closest primate relatives.
Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.
A neuronal ensemble is a population of nervous system cells involved in a particular neural computation.
Neural binding is the neuroscientific aspect of what is commonly known as the binding problem: the interdisciplinary difficulty of creating a comprehensive and verifiable model for the unity of consciousness. "Binding" refers to the integration of highly diverse neural information in the forming of one's cohesive experience. The neural binding hypothesis states that neural signals are paired through synchronized oscillations of neuronal activity that combine and recombine to allow for a wide variety of responses to context-dependent stimuli. These dynamic neural networks are thought to account for the flexibility and nuanced response of the brain to various situations. The coupling of these networks is transient, on the order of milliseconds, and allows for rapid activity.
The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct visual systems. Recently there seems to be evidence of two distinct auditory systems as well. As visual information exits the occipital lobe, and as sound leaves the phonological network, it follows two main pathways, or "streams". The ventral stream leads to the temporal lobe, which is involved with object and visual identification and recognition. The dorsal stream leads to the parietal lobe, which is involved with processing the object's spatial location relative to the viewer and with speech repetition.
The neural correlates of consciousness (NCC) are the minimal set of neuronal events and mechanisms sufficient for the occurrence of the mental states to which they are related. Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena; that is, neural changes which necessarily and regularly correlate with a specific experience. The set should be minimal because, under the materialist assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components are necessary to produce it.
Michael Steven Anthony Graziano is an American scientist and novelist who is currently a professor of Psychology and Neuroscience at Princeton University. His scientific research focuses on the brain basis of awareness. He has proposed the "attention schema" theory, an explanation of how, and for what adaptive advantage, brains attribute the property of awareness to themselves. His previous work focused on how the cerebral cortex monitors the space around the body and controls movement within that space. Notably he has suggested that the classical map of the body in motor cortex, the homunculus, is not correct and is better described as a map of complex actions that make up the behavioral repertoire. His publications on this topic have had a widespread impact among neuroscientists but have also generated controversy. His novels rely partly on his background in psychology and are known for surrealism or magic realism. Graziano also composes music including symphonies and string quartets.
The oddball paradigm is an experimental design used within psychology research. Presentations of sequences of repetitive stimuli are infrequently interrupted by a deviant stimulus. The reaction of the participant to this "oddball" stimulus is recorded.
Prefrontal synthesis is the conscious purposeful process of synthesizing novel mental images. PFS is neurologically different from the other types of imagination, such as simple memory recall and dreaming. Unlike dreaming, which is spontaneous and not controlled by the prefrontal cortex (PFC), PFS is controlled by and completely dependent on the intact lateral prefrontal cortex. Unlike simple memory recall that involves activation of a single neuronal ensemble (NE) encoded at some point in the past, PFS involves active combination of two or more object-encoding neuronal ensembles (objectNE). The mechanism of PFS is hypothesized to involve synchronization of several independent objectNEs. When objectNEs fire out-of-sync, the objects are perceived one at a time. However, once those objectNEs are time-shifted by the lateral PFC to fire in-phase with each other, they are consciously experienced as one unified object or scene.
Social cognitive neuroscience is the scientific study of the biological processes underpinning social cognition. Specifically, it uses the tools of neuroscience to study "the mental mechanisms that create, frame, regulate, and respond to our experience of the social world". Social cognitive neuroscience uses the epistemological foundations of cognitive neuroscience, and is closely related to social neuroscience. Social cognitive neuroscience employs human neuroimaging, typically using functional magnetic resonance imaging (fMRI). Human brain stimulation techniques such as transcranial magnetic stimulation and transcranial direct-current stimulation are also used. In nonhuman animals, direct electrophysiological recordings and electrical stimulation of single cells and neuronal populations are utilized for investigating lower-level social cognitive processes.
Posterior cortex usually means the posterior (back) part of the complete cerebral cortex and includes the occipital, parietal, and temporal cortices. In other words, the posterior cortex includes all the cerebral cortex without the frontal cortex.