Possible Glial Contribution in the Electrogenesis of SPs

The Neuroanatomy of Autobiographical Memory: A Slow Cortical Potential Study of Autobiographical Memory Retrieval☆

“…EPSPs giving rise to sustained negative shifts are thought to represent slow PSPs rather than summation of many short-lived EPSPs (e.g., Birbaumer et al, 1990). A role for glial depolarization (itself an index of neuronal activity) in the generation of SCPs has also been considered in models where glia are depolarized by extracellular potassium (e.g., Somjen, 1973Somjen, , 1975Caspers et al, 1987;Laming, 1989Laming, , 1993 perhaps aided by low resistance syncitium (e.g., Bauer et al, 1993). Overall these considerations indicate that large and relatively diffuse negative potentials at the cortical surface and far field potentials reaching the scalp are primarily a direct reflection of activity within underlying pyramidal neurons.…”

“…The term SCP is used to denote the fact that these potentials are predominantly cortical in origin. Slow potential shifts have a time course lasting from seconds to minutes (e.g., McCallum & Pleydell-Pearce, 1993) and perhaps up to hours (e.g., Bauer et al, 1993;Curry & Pleydell-Pearce, 1995;Pleydell-Pearce & Whitecross, 2000) and are usually absent in routine EEG recordings because they are removed by hardware or software filters (see Birbaumer et al, 1990, andRockstroh et al, 1989, for review). However, SCPs in the human EEG are increasingly used to make inferences about regional functional localization and this is because of the well-documented finding that negative SCP shifts recorded at the cortical surface reflect increased activation within underlying neural tissue, e.g.…”

Slow potential topography

“…If consecutive processing trials start before trial-specific initial baselines have been reached (which usually takes several seconds), new phasic shifts are added; in this way, they produce the tonic change. This has been shown by Bauer, Korunka, and M. Leodolter (1993), using a CNV paradigm and, recently, by means of topographic representation during spatial processing (Vitouch, Bauer, Gittler, M. Leodolter, & U. Leodolter, 1997). Figure 2 shows consecutive maps of SPSs that accompanied spatial processing of 13-sec median duration (varying within a range of 5 sec to 2 min) per trial.…”

Acoustic Noise Alters Selective Attention Processes as Indicated by Direct Current (DC) Brain Potential Changes

“…The origins of DC potentials and their shifts are–besides some contribution by glial cells [ 21 , 22 ]—considered to be mainly neuronal representing hypo- and hyperpolarization of pyramidal cells at their apical dendrites with underlying complex interactions between the cortex, thalamus, reticular formation, and the basal ganglia [ 21 , 22 , 23 ]. DC potential shifts may also be altered by changes in partial pressure of carbon dioxide (pCO 2 ) [ 24 ] and therefore by respiration rates [ 25 , 26 ].…”