Signals and signs in the nervous system: The dynamic anatomy of electrical activity is probably information-rich

Abstract

The dichotomy between two groups of workers on neuroelectrical activity is retarding progress. To study the interrelations between neuronal unit spike activity and compound field potentials of cell populations is both unfashionable and technically challenging. Neither of the mutual disparagements is justified: that spikes are to higher functions as the alphabet is to Shakespeare and that slow field potentials are irrelevant epiphenomena. Spikes are not the basis of the neural code but of multiple codes that coexist with nonspike codes. Field potentials are mainly information-rich signs of underlying processes, but sometimes they are also signals for neighboring cells, that is, they exert inf luence. This paper concerns opportunities for new research with many channels of wide-band (spike and slow wave) recording. A wealth of structure in time and three-dimensional space is different at each scale-micro-, meso-, and macroactivity. The depth of our ignorance is emphasized to underline the opportunities for uncovering new principles. We cannot currently estimate the relative importance of spikes and synaptic communication vs. extrasynaptic graded signals. In spite of a preponderance of literature on the former, we must consider the latter as probably important. We are in a primitive stage of looking at the time series of wide-band voltages in the compound, local field, potentials and of choosing descriptors that discriminate appropriately among brain loci, states (functions), stages (ontogeny, senescence), and taxa (evolution). This is not surprising, since the brains in higher species are surely the most complex systems known. They must be the greatest reservoir of new discoveries in nature. The complexity should not deter us, but a dose of humility can stimulate the f low of imaginative juices.A profound revolution lurks in our basic concept of how the information-bearing elements of the nervous system communicate. Two views coexist, mutually derogatory but not mutually exclusive, with little effort to discover the wider whole.* The dichotomy concerns such central questions about how brains work that I feel driven to put it under a spotlight.One common view, which we may dub the unit window, is that, with rare exceptions, neural communication consists of successions of nerve impulses in neurons, encoding messages in their intervals, decoding at axonal terminals into an analog dose of transmitter that restarts the cycle in the next cell. A principal problem in explaining higher functions is seen as the adequacy of sampling of units.The contrasting view, which we may call the population window, does not deny any of this except the implication that it embraces all the significant aspects of neural activity in organized cell assemblies. Major features of the dynamics of non-randomly assembled arrays, on this view, include their nonspike, more slowly fluctuating potentials, their changing degrees of population synchrony, and their rhythms and largescale patterns. These and other features are worth attention wh...

Natural world physical, brain operational, and mind phenomenal space–time

“…Further, oscillatory gamma responses were shown to be involved in visual perception and cognitive integrative function [250]. It is well established that EEG rhythms can modulate the excitability of neuronal cells changing the probability of their firing or dragging them into synchrony, hence influencing the coding of information [251]. Thus, different oscillatory patterns may be indicative of different information processing states; and it has been shown that the oscillatory patterns play an active role in these states [252,253].…”

Right ear advantage for vocal communication in frogs results from both structural asymmetry and attention modulation

“…Comparative EEG studies have shown that less EEG synchrony or more rapid coherence decline occur in reptiles, amphibians, and fish, respectively, in comparison to that of mammals [38]; thus power analysis rather than multivariate time-series analysis was selected for the current data. Prior to power spectrum analysis, for each frog and each channel, some representative and artifact-free segments (100 s) were selected randomly.…”

Systemic administration of the benzodiazepine receptor partial inverse agonist FG‐7142 disrupts corticolimbic network interactions

“…The LFP can be considered the vector sum of all (i.e., dendritic, somatic, axonal, synaptic) electrical activity in a relatively large volume (up to 1 mm 3 ) and is therefore attributable to both pre-and postsynaptic activity in many neurons in a given region (Bullock, 1997). Power spectra were generated from the 150 s epochs associated with each dose of FG-7142, using periodogram-based spectral estimation techniques (Halliday et al, 1995).…”