Generalized dimension of the intersection between EEGs

 The generalized dimension defined by [Mandelbrot (1995) J Fourier Anal Appl special J.P. Kahane issue: 409–432] was applied to studying the interrelationship between various parts of human cerebral cortex in different functional conditions. Taking EEG signals from different brain areas as different sets, the generalized dimensions of their intersections were calculated to describe the interrelationship between them. The results showed that the generalized dimensions of intersections in different brain states decreased according to the following order: rest with eyes open, closed, light sleep, and deep sleep. The generalized dimensions of intersections related to the left or right temporal lobe were higher than the others when the subjects was doing mental arithmetic, and there was a decrease when the subjects listened to soft classical music. In addition, it was found that there was a noticeable difference in singular spectra between epileptic patients and normal subjects, irrespective of whether the epileptic patient was experiencing a seizure or not. Received: 3 July 2000 / Accepted in revised form: 30 October 2000     

To what extent does land-use affect relationships between the distribution of woody species and climatic change? A case study along an aridity gradient in western Burkina Faso

The study aims at evaluating how land-use modifies the link between the observed distribution of species and the climatic variability and at detecting species involved in that modification. The area studied covers the phytogeographical transition between the South-Sudanian sector and the North-Sudanian sector in western Burkina Faso. It lies along an aridity gradient, of which the aridity index (UNESCO-MAB) ranges from 0.363 to 0.533. The data studied were derived from observations performed on 192 woody species in 603 vegetation survey plots inside and outside protected areas. The species turn-over (β diversity) and the mutual information were assessed along the aridity gradient inside protected areas on one hand and outside protected areas on the other. Our study shows that the statistical links between the geographical distributions of species and the aridity gradient differ according to whether the observations are performed inside or outside the protected areas. Anthropogenic disturbances, mainly agricultural in the region of study, result in a decrease in the β diversity and in the average mutual information between the distribution of all the woody species and the climatic gradient. Moreover, the variation in mutual information differs according to the species: it diversely decreases with agricultural land-use for most of them, but increases for some. Thus, land-use leads to species-specific changes in the realised climatic niches.     

Response to commentaries on “The Transmission Sense of Information”

Biologists rely heavily on the language of information, coding, and transmission that is commonplace in the field of information theory developed by Claude Shannon, but there is open debate about whether such language is anything more than facile metaphor. Philosophers of biology have argued that when biologists talk about information in genes and in evolution, they are not talking about the sort of information that Shannon’s theory addresses. First, philosophers have suggested that Shannon’s theory is only useful for developing a shallow notion of correlation, the so-called “causal sense” of information. Second, they typically argue that in genetics and evolutionary biology, information language is used in a “semantic sense,” whereas semantics are deliberately omitted from Shannon’s theory. Neither critique is well-founded. Here we propose an alternative to the causal and semantic senses of information: a transmission sense of information, in which an object X conveys information if the function of X is to reduce, by virtue of its sequence properties, uncertainty on the part of an agent who observes X. The transmission sense not only captures much of what biologists intend when they talk about information in genes, but also brings Shannon’s theory back to the fore. By taking the viewpoint of a communications engineer and focusing on the decision problem of how information is to be packaged for transport, this approach resolves several problems that have plagued the information concept in biology, and highlights a number of important features of the way that information is encoded, stored, and transmitted as genetic sequence.     

Desynchronization α frequency event-related in visual selective attention requiring tasks

Comparative analysis of the EEG amplitude depression in the α band has been performed in two paradigms varying in the degree of involvement of functionally different attention processes: visual search for the relevant stimulus (RS) among many irrelevant stimuli (iRS) and oddball. Simple visual examination of several identical stimuli was used as a control for the visual search task. The method of videooculography was used for verification of gaze direction during RS search. The EEG dynamics in the α band (desynchronization, D) was considered to be a correlate of attention processes. The visual search task performance revealed considerably higher D after RS finding compared to the control. The higher degree of D during the search seems to be due to the higher complexity of the task and complexity of visual environment. The D in the frontal regions, which has the greatest amplitude, supposedly reflects the performance of an adequate motor performance program under the control of voluntary (top-down) attention. At the same time, the D in the occipital and parietal areas seems to reflect the processes of involuntary attention activated due to the change in visual information (the finding of the only RS among numerous iRS). In the oddball task, presentation of both RS and iRS also induced D, which proved to be more marked in response to RS and maximal in the visual areas. We suppose that D under oddball reflects the involvement of involuntary attention.     

On the comparison of Feller and Ornstein-Uhlenbeck models for neural activity

 Diffusion processes have been extensively used to describe membrane potential behavior. In this approach the interspike interval has a theoretical counterpart in the first-passage-time of the diffusion model employed. Since the mathematical complexity of the first-passage-time problem increases with attempts to make the models more realistic it seems useful to compare the features of different models in order to highlight their relative performance. In this paper we compare the Feller and Ornstein–Uhlenbeck models under three different criteria derived from the level of information available about their parameters. We conclude that the Feller model is preferable when complete knowledge of the characterizing parameters is assumed. On the other hand, when only limited information about the parameters is available, such as the mean firing time and the histogram shape, no advantage arises from using this more complex model. Received: 8 November 1994/Accepted in revised form : 23 May 1995     

Early cortical specialization for face-to-face communication in human infants

This study examined the brain bases of early human social cognitive abilities. Specifically, we investigated whether cortical regions implicated in adults' perception of facial communication signals are functionally active in early human development. Four-month-old infants watched two kinds of dynamic scenarios in which a face either established mutual gaze or averted its gaze, both of which were followed by an eyebrow raise with accompanying smile. Haemodynamic responses were measured by near-infrared spectroscopy, permitting spatial localization of brain activation (experiment 1), and gamma-band oscillatory brain activity was analysed from electroencephalography to provide temporal information about the underlying cortical processes (experiment 2). The results revealed that perceiving facial communication signals activates areas in the infant temporal and prefrontal cortex that correspond to the brain regions implicated in these processes in adults. In addition, mutual gaze itself, and the eyebrow raise with accompanying smile in the context of mutual gaze, produce similar cortical activations. This pattern of results suggests an early specialization of the cortical network involved in the perception of facial communication cues, which is essential for infants' interactions with, and learning from, others.     

Defining and explaining culture (comments on Richerson and Boyd, Not by genes alone)

We argue that there is a continuum of cases without any demarcation between more individual and more cultural information, and that therefore “culture” should be viewed as a property that human mental representations and practices exhibit to a varying degree rather than as a type or a subclass of these representations and practices (or of “information”). We discuss the relative role of preservative and constructive processes in transmission. We suggest a revision of Richerson and Boyd’s classification of the forces of cultural evloution.     

Non-thermal signals govern selective brain cooling in pigs

We used implanted miniature data loggers and fine thermistors to measure arterial blood and brain temperatures in four female pigs, to a resolution of 0.04 °C, every 5 min, for 4 weeks. Within that period, pigs were exposed on different days, and in random order, to a cold (5 °C) or hot (38 °C) environment. In the thermoneutral environment of the pigs' home pens, brain temperature was usually lower than blood temperature. Such selective brain cooling was absent for 2 days after surgery, during handling and transport stress, and on waking. The magnitude of selective brain cooling was greatest when pigs were sleeping and body temperatures were low, and was smallest, or even absent, during hyperthermia and natural fever. Our results showed that selective brain cooling was present in pigs, but there was no clear relationship between blood temperature and the magnitude of selective brain cooling. Instead, the degree of selective brain cooling in pigs was governed by non-thermal factors, especially those associated with high sympathetic nervous system activity. Our results further support the concept that selective brain cooling does not serve to protect the brain from thermal damage during heat stress. Accepted: 14 September 1999     

老化和精神疾病引起的皮层抑制功能变化

脑神经网络信息加工的实现方式主要依赖于兴奋性和抑制性突触连接.脑内抑制性神经元数量较少,但在信息加工和神经可塑性等方面作用极其重要,而且抑制系统失常与多种脑功能障碍有关联.脑内抑制性神经环路可粗略分为皮层内和皮层间(包括前馈和反馈)两种,分别介导同一脑区内和不同脑区间的抑制作用.本文先围绕中心-外周抑制和运动方向互斥介绍了皮层间、皮层内抑制的行为表现和作用机制,然后以老化和精神疾病为例综述了脑功能障碍与视觉系统皮层抑制功能变化间的联系,希望能对相关研究工作有所助益.     

Activation and inhibitory types of brain neuronal sinchronisation: genesis and functional significance

The generalization of studies of the systemic work of cortical neurons during the information processing initiated in Livanov's laboratory allows us to make the following conclusions in terms of the modem state of the problem. In different brain structures, there is a considerable degree of correlation between neuronal activities and slow potential oscillations. In the state of rest or deep extinction, the synchronization of brain neurons increases by the inhibitory type. In the active state of the brain, the degree of neuronal synchronization increases by the activation type. Both processes are determined by the involvement of the whole brain inhibitory or activation systems, respectively. A relative augmentation of inhibitory processes results in a restriction of information transmission in the cortex and prevents its fixation in memory of the system. A decrease in inhibition facilitates the excitation thransmission in the interconnected brain structures. Synchronous convergence of ordered polse flows ensures the information fixation during learning.     

Multiform wave organization of neurophysiological processes-universal “language” of human brain in realization of informational-controlling functions

The paper summarizes literature data and results of many-year Laboratory studies disclosing principles of the multiform spatial-time organization of differing by rates of neurophysiologic brain processes as the universal “language” of its informational-controlling functions. There are considered current concepts of electrogenesis and physiological significance of ratios of gradual changes of biopotentials and impulse activity of neurons considered in studies of cerebral mechanisms of regulation of normal and pathological states, and organization of human psychic activity. Put forward and argumented are concepts of the probability principle of hierarchical organization of differing by rates of neurophysiologic processes brain zones, structures, and areas in formation of the brain systems participating in provision of the higher psychic functions and states. It is proposed to discuss the concept of the brain as the “swimming,” many-contour, neurodynamic informational-controlling suprasystem with universal, hierarchically organized neurodynamic structures—”functional organs” by A.A. Ukhtomskii (1978), of which formation provides large informational brain capacity and a wide specter of adaptive possibilities of the human organism.     

Biosemiosis and the Cellular Basis of Mind

The human brain is a complex organ made up of neurons and several other cell types, and whose role is processing information for use in elicitation of behaviors. To accomplish this, the brain requires large amounts of energy, and this energy is obtained by the oxidation of glucose (Glc). However, the question of how the oxidation of Glc by individual neurons in brain results in their collective ability to rapidly generate feats of cognition that allow them to recognize the nature of the universe in which they live and to communicate this information remains unclear. In this article, insights into this process are provided by first considering the brain’ s homeostatic “operating system” for supply of energy to stimulated neurons, and how this system defines the basic unit of brain “structure”. This is followed by consideration of the brain’s “two-cell” neuronal communication mechanism which defines the basic unit of brain “function”. Finally, an analysis of the nature of frequency-encoded “neuronal languages” that enable ensembles of neurons to translate energy derived from the oxidation of Glc into a collective “mind”, the aggregate of all brain processes including those involving perception, thought, insight, foresight, imagination and behavior.     

Foraging guilds of aquatic birds on productive boreal lakes: environmental relations and concordance patterns

Previous studies have shown that when an ecosystem consists of many interacting components it becomes impossible to understand how it functions by focussing only on individual relationships. Alternatively, one can attempt to quantify system behaviour as a whole by developing ecological indicators that combine numerous environmental factors into a single value. One such holistic measure, called the system ‘ascendency’, arises from the analysis of networks of trophic exchanges. It deals with the joint quantification of overall system activity with the organisation of the component processes and can be used specifically to identify the occurrence of eutrophication. System ascendency analyses were applied to data over a gradient of eutrophication in a well documented small temperate intertidal estuary. Three areas were compared along the gradient, respectively, non eutrophic, intermediate eutrophic, and strongly eutrophic. Values of other measures related to the ascendency, such as the total system throughput, development capacity, and average mutual information, as well as the ascendency itself, were clearly higher in the non-eutrophic area. When the whole-system properties of the three areas were compared, however, the values associated with the intermediate eutrophic area turned out to be the lowest, which possibly could be attributed to the unstable nature of this area. The current study provided an example of how the measures arising out of␣network analysis might lead to an improved understanding of the system functioning and of the eutrophication process itself.     

From symbolism to information? – Decoding the gene code

‘Information’ and ‘code’ originated as technical terms within linguistics and information theory but are now widely used in genetics and developmental biology. Against this background, it is examined if coded information distinguishes genes from other information carriers, i.e., whether there are genetic words or sentences by virtue of the genetic code, and, if so, whether they have any semantic content. It is concluded that there is no genetic language with semantic content, but that the genetic code still enables unique language-like modes of transmission and interpretation of causal information.     

Complexity of Multi-Dimensional Spontaneous EEG Decreases during Propofol Induced General Anaesthesia

Emerging neural theories of consciousness suggest a correlation between a specific type of neural dynamical complexity and the level of consciousness: When awake and aware, causal interactions between brain regions are both integrated (all regions are to a certain extent connected) and differentiated (there is inhomogeneity and variety in the interactions). In support of this, recent work by Casali et al (2013) has shown that Lempel-Ziv complexity correlates strongly with conscious level, when computed on the EEG response to transcranial magnetic stimulation. Here we investigated complexity of spontaneous high-density EEG data during propofol-induced general anaesthesia. We consider three distinct measures: (i) Lempel-Ziv complexity, which is derived from how compressible the data are; (ii) amplitude coalition entropy, which measures the variability in the constitution of the set of active channels; and (iii) the novel synchrony coalition entropy (SCE), which measures the variability in the constitution of the set of synchronous channels. After some simulations on Kuramoto oscillator models which demonstrate that these measures capture distinct ‘flavours’ of complexity, we show that there is a robustly measurable decrease in the complexity of spontaneous EEG during general anaesthesia.     

Psychophysiological and neurophysiological features of the organization of visuo-spatial performance in right-handed and left-handed six- to seven-year-old children

The developmental features of individual components of the visual perception and brain functional organization during visuo-spatial activity of different complexity were studied in right-handed and left-handed 6–7-year-old children. The results of psychophysiological testing of their visual perception testify to the underdevelopment of the mechanisms of integrative brain activity. Some specific features of the brain functional organization were revealed in the left-handed children during visuo-spatial performance. More autonomous functioning of the cerebral hemispheres and the duplication of the activation processes in the right and left hemisphere during visuo-spaital performance of different complexity are characteristic of these children. This is probably associated with the involvement of compensatory mechanisms, which enable the performance reliability.     

Analysis of phase-locking is informative for studying event-related EEG activity

 A new method is presented for quantitative evaluation of single-sweep phase and amplitude electroencephalogram (EEG) characteristics that is a more informative approach in comparison with conventional signal averaging. In the averaged potential, phase-locking and amplitude effects of the EEG response cannot be separated. To overcome this problem, single-trial EEG sweeps are decomposed into separate presentations of their phase relationships and amplitude characteristics. The stability of the phase-coupling to stimulus is then evaluated independently by analyzing the single-sweep phase presentations. The method has the following advantages: information about stability of the phase-locking can be used to assess event-related oscillatory activity; the method permits evaluation of the timing of event-related phase-locking; and a global assessment and comparison of the phase-locking of ensembles of single sweeps elicited in different processing conditions is possible. The method was employed to study auditory alpha and theta responses in young and middle-aged adults. The results showed that whereas amplitudes of frequency responses tended to decrease, the phase-locking increased significantly with age. The synchronization with stimulus (phase-locking) was the only parameter reliably to differentiate the brain responses of the two age groups, as well as to reveal specific age-related changes in frontal evoked alpha activity. Thus, the present approach can be used to evaluate dynamic brain processes more precisely. Received: 12 February 1996 / Accepted in revised form: 11 October 1996     

Glutamate antibodies repress expression of <Emphasis Type="Italic">Dffb</Emphasis> gene in brain of rats in experimental Alzheimer’s disease

The rat model of Alzheimer’s disease including injection of neurotoxic fragment of β-amyloid protein Aβ_25–35 into giant-cell nuclei basalis of Meynert was used for experiments. We have investigated the influence of glutamate antibodies administered intranasally in a dose of 300 μg/kg after 1 h of the mentioned alteration on the level of expression of Dffb mRNA. Dffb gene codes caspase-dependent DNase, which participates in the internucleosomal fragmentation of genome DNA during apoptosis. On the third day after the injection of Aβ_25–35, we obtained a significant decrease in Dffb gene expression in the prefrontal cortex (37% decrease) and hippocampus (62% decrease) in the group of experimental animals compared to the control group. In the hypothalamus, there were no such differences. Seemingly, the repressing action of glutamate antibodies on the mRNA expression of the Dffb gene reflects the stabilization of processes that take place in the brain cells during experimental Alzheimer’s disease; meanwhile, the intensity of the apoptotic death of neurons and glial cells decreases.     

Inhibition in Adults with Attention Deficit/Hyperactivity Disorder: Event-Related Potentials in the Stop Task

The core deficit in Attention Deficit/Hyperactivity Disorder (ADHD) may be a deficiency in executive functions, particularly the processes that are associated with the inhibition of predominant responses. To test this notion in the adult population, healthy undergraduate volunteers and students with ADHD symptoms performed a visual Stop Signal Task (Logan et al. J Exp Psychol: Hum Percept Perform 10:276–291, 1984) while Event-Related brain Potentials were recorded. The two groups did not differ on behavioral measures of performance, but there was a significant difference in the N2–P3 component. These results underline the robustness of an N2–P3 difference between healthy adults and people with ADHD symptoms that have persisted into young adulthood.     

Analysis of long range dependence in the EEG signals of Alzheimer patients

Alzheimer’s disease (AD), a cognitive disability is analysed using a long range dependence parameter, hurst exponent (HE), calculated based on the time domain analysis of the measured electrical activity of brain. The electroencephalogram (EEG) signals of controls and mild cognitive impairment (MCI)-AD patients are evaluated under normal resting and mental arithmetic conditions. Simultaneous low pass filtering and total variation denoising algorithm is employed for preprocessing. Larger values of HE observed in the right hemisphere of the brain for AD patients indicated a decrease in irregularity of the EEG signal under cognitive task conditions. Correlations between HE and the neuropsychological indices are analysed using bivariate correlation analysis. The observed reduction in the values of Auto mutual information and cross mutual information in the local antero-frontal and distant regions in the brain hemisphere indicates the loss of information transmission in MCI-AD patients.