Hippocampus as a wormhole: gateway to consciousness.

Commentary on: Faw M, Faw B. Neurotypical subjective experience is caused by a hippocampal simulation. WIREs Cogn Sci 2017, e1412.

Mind-body problem and hippocampus.

Commentary on Faw's comprehensive response to a previous commentary ('Hippocampus as a wormhole' by Ralf-Peter Behrendt, doi: 10.1002/wcs.1446) on Faw and Faw's paper (doi: 10.

Hallucinatory experience as aberrant event memory formation: Implications for the pathophysiology of schizophrenia.

If hallucinations are not fundamentally different from normal wakeful experiences, then the neural basis of hallucinations has to be essentially that of consciousness in general. The additional insight that consciousness reflects the formation (as opposed to consolidation) of event (episodic) memories links the pathophysiology of hallucinations to the hippocampus. Perceptions and misperceptions, insofar as they are consciously experienced, constitute contextualized and unitary phenomena (which are embedded as discrete events in the stream of consciousness); they are experiential manifestations of activity patters that recurrently emerge in the CA3 network of the hippocampus (and that are secondarily consolidated into retrievable and declarable memories).

Situationally appropriate behavior: translating situations into appetitive behavior modes.

If an organism's responding to its present location or more abstract situation is similar to its responding to discrete motivationally salient stimuli, then principles of stimulus-response relationships and their acquisition may apply to the organization of behavior that appears to be sensitive and appropriate to the organism's external context. Locations or situations become motivationally salient, insofar as they acquire the ability to compel the organism to obtain a specific type of reward through more or less constrained exploratory or foraging behavior. The ventral hippocampus is proposed to play a key role in linking a salient situation or location with an appropriate mode of behavior, whereas allocentric information predicted and updated by the dorsal hippocampus may be associated with, or translated into, a sequence of orienting and locomotor actions.

Conscious experience and episodic memory: hippocampus at the crossroads.

If an instance of conscious experience of the seemingly objective world around us could be regarded as a newly formed event memory, much as an instance of mental imagery has the content of a retrieved event memory, and if, therefore, the stream of conscious experience could be seen as evidence for ongoing formation of event memories that are linked into episodic memory sequences, then unitary conscious experience could be defined as a symbolic representation of the pattern of hippocampal neuronal firing that encodes an event memory - a theoretical stance that may shed light into the mind-body and binding problems in consciousness research. Exceedingly detailed symbols that describe patterns of activity rapidly self-organizing, at each cycle of the θ rhythm, in the hippocampus are instances of unitary conscious experience that jointly constitute the stream of consciousness. Integrating object information (derived from the ventral visual stream and orbitofrontal cortex) with contextual emotional information (from the anterior insula) and spatial environmental information (from the dorsal visual stream), the hippocampus rapidly forms event codes that have the informational content of objects embedded in an emotional and spatiotemporally extending context.

Hippocampus and consciousness.

An important assumption concerning the physiology of consciousness is that all varieties of conscious experience are closely related to each other and, hence, are subserved by the same neural mechanism. There are several considerations that lead us to implicate the hippocampus in the generation of conscious perception and, ultimately, of conscious experiences of all kinds. Firstly, conscious perception of external events is intricately linked with the formation of episodic (declarative) memories, a key function attributed to the hippocampus.

Contribution of hippocampal region CA3 to consciousness and schizophrenic hallucinations.

Recent advances in understanding hippocampal information processing offer new vistas on the mind-body and binding problems. Information encoded by the autoassociation network of cornu ammonis 3 (CA3) situates landmarks and objects within an allocentric framework of space and time. Guiding locomotion across the spatial environment, and generally organizing behaviour that transcends space and time, the hippocampus creates phenomenal space and time themselves, thus laying the foundations for conscious awareness.

Vocalisation in verbal hallucinations: case report and theoretical model.

Perception of one's speech or the speech of others reflects an intrinsic process and should not to be seen as a product of information processing of external sensory input. From this perspective, the perception of one's own or others' speech is fundamentally equivalent to the experience of verbal hallucinations. Speech perception is generated primarily in the focus of attention, but auditory and proprioreceptive input from verbal articulations play an important constraining role, ensuring that perception remains adaptive to interaction with the external world.

Dysregulation of thalamic sensory "transmission" in schizophrenia: neurochemical vulnerability to hallucinations.

Cholinergic arousal mechanisms predispose thalamic and cortical neurons to fire action potentials at gamma rhythms, which have a tendency to resonate in thalamocortical networks, thereby forming coherent assemblies under constraints of sensory input to specific thalamic nuclei, on the one hand, and prefrontal and limbic attentional mechanisms, on the other. Perception may be based on sustained assemblies of coherent gamma oscillations in thalamocortical circuits. In schizophrenia, the impact of sensory input on self-organization of thalamocortical activity may be generally reduced.

Hallucinations in schizophrenia, sensory impairment, and brain disease: a unifying model.

Based on recent insight into the thalamocortical system and its role in perception and conscious experience, a unified pathophysiological framework for hallucinations in neurological and psychiatric conditions is proposed, which integrates previously unrelated neurobiological and psychological findings. Gamma-frequency rhythms of discharge activity from thalamic and cortical neurons are facilitated by cholinergic arousal and resonate in networks of thalamocortical circuits, thereby transiently forming assemblies of coherent gamma oscillations under constraints of afferent sensory input and prefrontal attentional mechanisms. If perception is based on synchronisation of intrinsic gamma activity in the thalamocortical system, then sensory input to specific thalamic nuclei may merely play a constraining role.

A neuroanatomical model of passivity phenomena.

Any attempt to elucidate the nature and mechanism of passivity phenomena, i.e., experiences that one's conscious actions or thoughts have not been 'willed' by oneself, requires an integrative philosophical-neurobiological approach.