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PubMed2000

Taking perspective in conversation: the role of mutual knowledge in comprehension.

When people interpret language, they can reduce the ambiguity of linguistic expressions by using information about perspective: the speaker's, their own, or a shared perspective. In order to investigate the mental processes that underlie such perspective taking, we tracked people's eye movements while they were following instructions to manipulate objects. The eye fixation data in two experiments demonstrate that people do not restrict the search for referents to mutually known objects. Eye movements indicated that addressees considered objects as potential referents even when the speaker could not see those objects, requiring addressees to use mutual knowledge to correct their interpretation. Thus, people occasionally use an egocentric heuristic when they comprehend. We argue that this egocentric heuristic is successful in reducing ambiguity, though it could lead to a systematic error.

Adult↗

PubMed2006

The relationship of theory and methodology in EEG studies of mental activity.

Due to the multidisciplinary character of psychophysiology, the problem of comparability of psychological and physiological phenomena of different natures and levels of organization has always been raised. This requires the interaction of theory and methodology to appropriately address the specifics of the psychophysiological paradigm, all the while maintaining their grounding in the actual psychological and physiological concepts. The history of EEG studies of mental activity shows that a weak theoretical basis at certain stages can result not only in methodological crises but can also affect empirical data collection and interpretation. An adequate theory can lend strong support to the methodology with "brain-oriented" structuring of psychological tasks and such a theory improves the neurophysiological informative value of the EEG parameters referring to the psychological characteristics of mental processes etc. On the other hand, the great importance of the EEG recording and processing techniques can result in overrating technological progress, hence frequently holding back meaningful interpretation and construction of a comprehensive psychophysiological conceptual framework. This in turn causes demands for higher material and intellectual outlays, due to overspecialization in research, and results in work duplication as well as the creation of a fragmentary knowledge structure. This article illustrates how the multidisciplinary interaction of theory and methodology, when focused on theoretical problems, can yield a series of concepts with escalating levels of integration, bringing together such different branches of psychophysiology as the study of functional states and of individual differences. As a result, this extends the theoretical model based on normal material to encompass borderline constitutional psychopathology.

Electroencephalography↗

PubMed1998

Interpreting functional imaging studies in terms of neurotransmitter cycling.

Functional imaging experiments, in particular positron-emission tomography and functional magnetic resonance imaging, can be analyzed either in psychological terms or on the basis of neuroscience. In the usual psychological interpretation, stimulations are designed to activate specific mental processes identified by cognitive psychology, which are then localized by the signals in functional imaging experiments. An alternate approach would be to analyze experiments in terms of the neurobiological processes responsible for the signals. Recent in vivo 13C NMR measurements of the glutamate-to-glutamine neurotransmitter cycling in rat and human brains facilitate a neuroscientific interpretation of functional imaging data in terms of neurobiological processes since incremental neurotransmitter flux showed a 1:1 stoichiometry with the incremental rate of glucose oxidation. Because functional imaging signals depend on brain energy consumption, a quantitative relationship can be established between the signal (S) and the specific neurochemical cerebral neurotransmitter activity (N) of glutamate-to-glutamine neurotransmitter cycling. The quantitation of neuronal activity proposed has implications for the psychological design and interpretation of functional imaging experiments. Measurements of the neurotransmitter cycling flux at rest in functional imaging experiments suggest that performing cognitive tasks and sensory stimulations increases neurotransmitter cycling by only 10-20%. Therefore it cannot be assumed that reference state activities are negligible, nor that they are constant during stimulation.

Animals↗

PubMed2003

Quantitative EEG patterns following unilateral stroke: a study in chronic stage.

The aim of this study was to investigate the EEG power spectra obtained during rest and mental processing in chronic stroke patients. Seventeen patients with stabilized unilateral cerebral ischemia, grouped according to the side of lesion, underwent quantitative EEG recordings during rest and attentive/cognitive tasks. EEG spectral values were compared with those of 11 healthy subjects. Patients displayed different EEG patterns from controls, under rest condition: patients with left hemispheric lesion were characterized by a preserved alpha and beta band "reactivity," with a lack of significant changes in slow band components. In patients with right hemisphere lesion, no significant changes of the slow and fast band activities were evident during each task. These findings indicate that different EEG patterns of activation characterize stroke patients with left and right hemispheric damage.

Aged↗

PubMed1996

Intention as a component of the alpha-rhythm response to mental activity.

Many studies of alpha-rhythm reactivity conclude that alpha is selectively attenuated by attention accompanying mental activity. The topography of this attenuation is assumed to match the relevant functional topography of the cortex. But there are reports of apparent increased attention resulting in no change, or even enhanced alpha - the paradoxical response. It is proposed that in this case, alpha amplitude may be dependent on an intention component of behaviour. Some conflicting reports of alpha reactivity to mental processes may then be resolved. It is argued that the classical attention model of alpha is untenable, except for simple sensori-motor responses. Reasons are given to support this and the concept of intention as a neuropsychological variable is introduced. Evidence is presented for a generalisation of an oculomotor model of alpha activity proposed by Wertheim who demonstrated that alpha reduces during attentive, but not during intentive visual behaviour. The generalisation follows from reports of enhanced alpha in the few seconds prior to a skilled action in sport, and by neurophysiological evidence for a separate cortical organisation for perception and action. Varying proportions of attention and intention then add a dimension to the factors influencing alpha blocking which may explain its inconsistent response.

Adult↗

PubMed2003

CSF galanin and cognition after shunt surgery in normal pressure hydrocephalus.

BACKGROUND: "Normal" pressure hydrocephalus (NPH) is associated with injury to neurotransmitter and neuropeptide systems that recovers after surgery. This could be linked to changes in galanin, a neuropeptide with inhibitory effects on basal forebrain cognitive function. OBJECTIVE: To examine changes in CSF galanin concentrations in patients with normal pressure hydrocephalus undergoing shunt surgery, and to investigate the relation between these changes and cognitive functioning. METHODS: Eight patients underwent surgery for idiopathic normal pressure hydrocephalus. Lumbar CSF galanin determinations, cognitive status, and clinical status were quantified before operation and six months after. Cognition was assessed by an extensive battery of tests measuring attention, memory, speed of mental processing, visuospatial function, and frontal lobe function. RESULTS: CSF galanin concentration decreased after surgery. This reduction correlated with improved clinical and cognitive functioning, specifically with attention and visuomotor speed, visuoconstructive and frontal functioning, and clinical status according to the NPH scale, including the sphincter and cognitive components. CONCLUSIONS: The cognitive and clinical improvement after shunt implantation correlated with CSF galanin levels, suggesting that the distribution or function of this agent involves cerebral structures that have some potential for recovery. In this study, galanin was related to several cognitive functions that may be associated with the fronto-subcortical deficits underlying cognitive dysfunction in normal pressure hydrocephalus.

Aged↗

PubMed2004

Effects of acute and repeated administration of a cholinesterase inhibitor on timing behaviour.

It has been hypothesised that a leftward shift in the response distribution obtained in the peak interval (PI) procedure is a characteristic of cognitive enhancement in which mental processes are speeded. Metrifonate, a cholinesterase inhibitor with reported cognitive enhancing properties in many animal models of learning and memory, was tested in the PI procedure. Acute administration of 3 and 60 mg/kg but not 1 and 30 mg/kg in fully trained rats shifted the response distribution to the right, whereas subchronic administration of 10, 30 or 50 mg/kg during task acquisition had no effect on timing behaviour. On the basis of the present data, it can be concluded that the effects of a cognition enhancer in the PI procedure cannot be predicted from the scalar expectancy theory (SET). Furthermore, SET does not appear to be an appropriate tool for analysing the acquisition of timing behaviour.

Animals↗

PubMed1985

[The effect of a new analgesic, flupirtine, on psychomotor performance in humans].

Psychomotor efficiency was tested on 12 male patients after peroral administration of the analgesically acting monosubstance 2-amino-3-ethoxycarbonyl-amino-6-p-fluorobenzyl aminopyridine (flupirtine, Katadolon) (3 X 100 mg on the previous day and 100 mg before the test) and compared with the peroral administration of diazepam, chlorphenoxamine and a placebo using a combined multiple problem, which tests the fine motor coordination in the peripheral and central field of vision at high vigilance. Compared with the placebo, flupirtine lengthened the reaction time with only slight significance by 2.7 +/- 2.2%, but with significance the mental processing time by 3.0 +/- 1.9%. This sedative effect reached only 41% and 43% respectively of the sedative effect of the antihistamine chlorphenoxamine (80 mg daily dose on the preceding day and 20 mg 1 h before start of the test). Under the hangover effect of diazepam (evenings 10 mg perorally 2 days before and 5 mg perorally on the preceding day) slightly significant shorter times were determined than under flupirtine. Flupirtine does not change the number of standard errors and the uniformity of performance, but it does increase the number of signals overlooked in the experiment, to a considerably lesser degree, however, than chlorphenoxamine. In the hangover of diazepam, the number of standard errors is lower and the number of overlooked signals greater than under flupirtine. The errors and the number of overlooked signals are greatest under chlorphenoxamine.

Aminopyridines↗

PubMed1993

Drawing the boundary between subject and object: comments on the mind-brain problem.

Physics says that it cannot deal with the mind-brain problem, because it does not deal in subjectivities, and mind is subjective. However, biologists (among others) still claim to seek a material basis for subjective mental processes, which would thereby render them objective. Something is clearly wrong here. I claim that what is wrong is the adoption of too narrow a view of what constitutes 'objectivity', especially in identifying it with what a 'machine' can do. I approach the problem in the light of two cognate circumstances: (a) the 'measurement problem' in quantum physics, and (b) the objectivity of standard mathematics, even though most of it is beyond the reach of 'machines'. I argue that the only resolution to such problems is in the recognition that closed loops of causation are 'objective'; i.e. legitimate objects of scientific scrutiny. These are explicitly forbidden in any machine or mechanism. A material system which contains such loops is called 'complex'. Such complex systems thus must possess non-simulable models; i.e. models which contain impredicativities or 'self-references' which cannot be removed, or faithfully mapped into a single coherent syntactic time-frame. I consider a few of the consequences of the above, in the context of thus redrawing the boundary between subject and object.

Biophysical Phenomena↗

PubMed2006

[Free will and neurobiology: a methodological analysis].

Whether or not the neurobiological basis of mental processes is compatible with the philosophical postulate of free will is a matter of committed debating in our days. What is the meaning of those frequently-quoted experiments concerning voluntary action? Both convictions, being autonomous subjects and exercising a strong influence on the world by applying sciences, have become most important for modern human self-conception. Now these two views are growing apart and appear contradictory because neurobiology tries to reveal the illusionary character of free will. In order to cope with this ostensible dichotomy it is recommended to return to the core of scientific thinking, i. e. to the reflection about truth and methods. The neurobiological standpoint referring to Libet as well as the philosophical approaches to free will must be analysed, considering pre-conceptions and context-conditions. Hence Libet's experiments can be criticised on different levels: methods, methodology and epistemology. Free will is a highly complex system, not a simple fact. Taking these very complicated details into account it is possible to define conditions of compatibility and to use the term free will still in a meaningful way, negotiating the obstacles called pure chance and determinism.

Brain↗

PubMed1962