Risto Näätänen talks abstracts

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Here you find the abstracts for Risto Näätänens two talks October 20th and 21st, 2015.

  1. THE MISMATCH NEGATIVITY (MMN) IN BASIC RESEARCH OF CENTRAL AUDITORY PROCESSING

One of the central tasks of the brain is to monitor its environment for possible sudden changes, which is of central importance for adaptive behavior, even survival. In the auditory modality, this vital function is reflected by the mismatch negativity (MMN; Naatanen et al. 1978), which is an electrophysiological response to any discriminable change in some repetitive aspect of the auditory input.

Further, the MMN has analogies in other brain-imaging modalities such as the magneto-encephalography (MEG), positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and optical imaging (OI), and can be recorded in the other sensory modalities also. In the auditory modality, this response, a component of the averaged event-related potential (ERP), is based on the sensory-memory traces or representations the brain is automatically forming for each repetitive aspect of the environmental stimulation (“standards”).

These neural traces, developed by this modelling function of the brain, usually last for a few seconds and, importantly, provide an objective index of the plasticity of the brain. Further, these representations undergo a change whenever there is a change in the ongoing stimulation automatically compared by the brain to these representations. This change elicits the MMN response representing the neural activity associated with the formation of a new representation.

Consistent with this, the MMN is larger in amplitude and peaks earlier for larger changes. The MMN-generation process is automatically and pre-perceptually initiated in the auditory cortex (the auditory-cortex MMN component) which process triggers a mainly right-hemispheric frontal activation (the frontal-cortex MMN component) associated with an involuntary attention switch to stimulus change usually leading to its conscious perception.

Consequently, the MMN enables one to probe the system of the short-term memory traces of the brain which underlie sensory memory.

These functions appear mainly to depend on the adequate functioning of the NMDA-receptor system, essential for the formation of memory traces and thus for cognitive performance. Moreover, the MMN enables one also to probe the long-term, or permanent, auditory memory traces of the brain such as those for familiar speech sounds, voices and musical melodies, hence giving an access to all the different, hierarchically organized levels of the representations of the auditory environment on all the different time scales. Therefore, among other things, the MMN also provides a very useful tool for studies of foreign-language learning, enabling one to monitor the development of new memory traces for the speech sounds of the new language, enabling the learner to correctly perceive these speech sounds. Moreover, recent studies have also shown that the MMN even opens windows to the neural changes associated with the perceiving and learning of the semantic meanings of speech sounds of the mother tongue and foreign languages.

Furthermore, the auditory MMN has analogies in all the other sensory modalities, too: the visual MMN (vMMN), the somatosensory MMN (sMMN), and the olfactory MMN (oMMN). Consequently, the MMN is, in fact, a universal manifestation of the second main task that the brain has on the perceptual side of its interaction with its environment, viz., the continuous up-dating of the environmental representations to correspond to environmental changes.

Moreover, importantly, recent MMN studies have also revealed a third, anticipatory, category of brain function in that the up-dated memory representations not only correspond to the sensory events of the immediate past but also automatically predict those of the immediate future on the basis of the sequential regularities automatically detected in the ongoing stimulus stream. These recent studies have therefore given rise to an extended view of the role of the sensory cortices in information processing, which are not only sensory but rather sensory-cognitive, in nature and hence demonstrate the presence of “primitive sensory intelligence”, a new major focus of cognitive brain research.

  1. THE MISMATCH NEGATIVITY (MMN): CLINICAL PERSPECTIVES

Recent studies have shown that the MMN provides a unique window to the brain´s ability  to form and maintain new memory traces, a central prerequisite for  adequate cognitive function, and thus serves, among other things, as an index of the adequate NMDA-reseptor system functioning of the brain. Consistent with this, recent studies have also revealed a large magnitude of clinical applications of the MMN which can be measured irrespective of attention and  co-operation of the person, a  particular asset in patient and infant work. The first of these clinical studies, conducted in Bristol, UK, demonstrated that if an MMN could be recorded in a comatose patient this predicted his/her recovery of consciousness in the near future and even the magnitude of the recovery of cognitive capacity. Subsequent studies, mainly conducted in Lyon, France, and Amsterdam, The Netherlands, showed that the MMN recorded at hospitalization could be used for predicting the patient´s chances of survival and that the MMN could also be used for on-line monitoring of the development of the patient´s state in the persistent vegetative state (PVS). As for schizophrenia, it was recently found that a very low amplitude of the MMN, especially of that to tone-duration prolongation, in clinically at-risk individuals predicted psychosis onset within the near future. Moreover, the MMN has also opened new perspectives in infant and child work in part because no attention or task performance is required for the objective assessment of the age-appropriate development of the central auditory system. In more general terms, a deficient MMN response reflects the magnitude of cognitive decline in a large number of different brain disorders such as schizophrenia, Alzheimer´s Disease and other dementias, Parkinson`s Disease, stroke, epilepsy, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), autism, Asperger`s Syndrome, Down`s Syndrome, Huntington`s Disease, Major Depression, and also in the so-called normal ageing. However, much progress still is to be made in recording and signal-analysis methods and procedures before the MMN really is ripe  as a tool for every-day work in hospitals and clinics, which depends on the quality of the individual-level  patient recordings and the associated signal-analysis procedures.