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PubMed2003

Properties of GABA(A) receptor-mediated transmission at newly formed Golgi-granule cell synapses in the cerebellum.

Cerebellar granule cells receive inhibitory synaptic input from Golgi cells, which is mediated by gamma-aminobutyric acid (GABA) acting on GABA(A) receptors. In the present study we examined the properties of GABAergic inhibitory postsynaptic currents (IPSCs) in granule cells of the rat at a time when they first receive synaptic contacts from Golgi cells. Our results demonstrate that granule cells receive functional GABAergic synaptic input as early as postnatal day three (P3). The kinetic properties of these early IPSCs and the single-channel conductance of the synaptic receptors are similar to those seen at the end of the first postnatal week, suggesting a stable subunit composition during this initial period of development. However, at P3, unlike the situation at more mature synapses, two distinct patterns of synaptic activity are evident, with IPSCs occurring either regularly or in bursts. In addition we find that Golgi cells are spontaneously active during early development, and at P7 most IPSCs are action potential-dependent. Moreover, paired Golgi-granule cell recordings suggest a high level of connectivity and a high release probability at these early synapses.

2-Amino-5-phosphonovalerate↗
PubMed1978

Responses and pharmacological properties of preoptic/anterior hypothalamic neurones following medial forebrain bundle stimulation.

1. The responses of neurones in the anterior hypothalamic and preoptic areas (POA/AHA) to stimulation of the medial forebrain bundle (MFB) have been studied in urethane anaesthetized female rats. Extracellular unit recordings have been made from 150 neurones which were responsive to a single stimulus applied to the MFB at the level of the mammillary nucleus. 2. Forty-five per cent of these cells were orthodromically activated with latencies ranging from 7.5 to 100 msec. However, the majority of cells responded with latencies of less than 40 msec. 3. Marked inhibition of spontaneous activity was observed in 41.5% of the units. Response latencies of up to 40 msec were observed in these cells, the inhibitory periods lasting up to 150 msec. 4. A small proportion of cells (13.5%) were antidromically activated and the average conduction velocity of these neurones in the POA/AHA with axons passing down to the mid-brain was estimated to be 0.3 m sec-1. It is suggested that they represent part of the descending MFB. 5. The experiments did not show any discrete topographical organization of cells in the POA/AHA which could be driven by MFB stimulation although the units tended to be located in more lateral rather than medial areas. 6. The responses to iontophoretically applied dopamine (DA) or noradrenaline (NA) was tested on sixty-one cells. These amines suppressed the activity of the majority of both orthodromically activated and inhibited units; the remaining cells were unresponsive. 7. These results provide electrophysiological evidence for both a direct and indirect input of MFB fibres to cells in the POA/AHA and that these inputs can be either excitatory or inhibitory. The data also indicate that a small number of fibres in the descending MFB originate from cells in the POA/AHA. 8. The sensitivity of these units to NA and DA suggests an inhibitory aminergic input, although this evidence is as yet indirect. 9. These connexions of the MFB, with neurones in the POA/AHA may be part of the neural circuits important for extra-hypothalamic modulation of gonadotrophin secretion.

Animals↗
PubMed1975

Patterns of projection and braching of reticulospinal neurons.

Extracellular microelectrodes were used to record the activity of reticulospinal neurons within the medial ponto-medullary reticular formation in the cat. In one series of experiments reticulospinal neurons were activated from electrodes in the ventro-medial reticulospinal tract (RSTm) and in the ipsi- and contralateral lateral reticulospinal tracts (RSTi, RSTc) at spinal levels C1--2, C4, Th1 and L1. RSTm neurons were found primarily in n.r. pontis caudalis and the rostro-dorsal part of n.r. gigantocellularis. 71% of these neurons projected as far as the lumbar spinal cord. RSTi neurons projecting to C4 and beyond were clustered in the caudo-ventral part of n.r. gigantocellularis, but those RSTi neurons projecting to the first three cervical segments were located more rostro-dorsally. In all, 63% of the RSTi neurons projected to the lumbar spinal cord. RSTc neurons, which comprised only 5% of the reticulospinal population, were found throughout n.r. gigantocellularis. RSTm neurons had a median conduction velocity of 101 m/sec whereas RSTi and RSTc had median conduction velocities on the order of 70 m/sec. In a second series of experiments microstimulation was used to activate branches of reticulospinal neurons within the gray matter of the cervical enlargement. Twenty-two of thirty-three neurons found to project to the cerivcal ventral horn were branching neurons that also sent axons to the lumbar spinal cord. Thus much of the teticulospinal activity reaching the cervical enlargement also acts at one or more other spinal levels. Detailed investigation of the course of reticulospinal axons within the cervical gray matter indicated that a single axon may traverse wide areas of the ventral horn including regions on both sides of the spinal cord.

Animals↗
PubMed1996

Activation of GABAB receptors at individual release boutons of the crayfish opener neuromuscular junction produces presynaptic inhibition.

1. Presynaptic inhibition in crustaceans involves the activation of gamma-aminobutyric acid-A (GABAA) receptors that produce an increase in chloride conductance at excitatory axon terminals. Such inhibition produced by single inhibitory pulses is blocked by picrotoxin, a GABAA antagonist. 2. Presynaptic inhibition produced by bath application of GABA was not blocked by picrotoxin. Measurements of the membrane resistance of the excitatory axon terminals revealed that substantial presynaptic inhibition still persisted after 50 microM picrotoxin had completely blocked the increase in conductance produced by 10 microM GABA. 3. Baclofen, a GABAB agonist, reduced release from the excitatory nerve terminals, and 20H-Saclofen, a GABAB antagonist, blocked the effect of baclofen and the presynaptic inhibition produced by 10 microM GABA. 4. 20H-Saclofen alone did not block presynaptic inhibition produced by 100 microM GABA, and the combined action of both 20H-Saclofen and picrotoxin was required to block such effects. 5. The excitatory nerve terminals seem to contain GABAA and GABAB receptors. The GABAB receptors are preferentially activated at lower GABA concentrations (in the microM range), whereas both the GABAA and GABAB receptors are activated at high GABA concentrations.

Animals↗
PubMed1995

Abnormal evoked potentials of Kearns-Sayre syndrome.

We examined eight patients with Kearns-Sayre syndrome (KSS) to investigate a dysfunction in the central nervous system (CNS) using PTN-SEP, MN-SEP and BAEP. We found a significant increase in the P37 latency of PTN-SEPs and the central conduction time of MN-SEPs, and interpeak latencies of BAEPs. Delayed SEPs or BAEPs were caused by a dysfunction of the somatosensory or lateral lemniscus pathways which could be related to mitochondrial abnormalities in the CNS. Long-term therapy with CoQ showed an improvement of the latencies of SEPs after about half a year from the start of CoQ therapy in our patients. The improvement of the latencies of SEPs were preserved during CoQ therapy. It could be demonstrated that CoQ therapy had the beneficial effects on abnormal functions of the CNS in patients with KSS.

Adult↗
PubMed1988

The morphology and projections of dorsal horn spinocerebellar tract neurones in the cat.

1. The morphology of dorsal horn neurones located in the mid-lumbar segments of the spinal cord and which have an axonal projection to the cerebellum has been investigated. The neurones were identified by antidromic activation from the cerebellum and by their characteristic input from group II afferents as described in the preceding paper (Edgley & Jankowska, 1988). 2. The cell bodies of the neurones were distributed across the width of the spinal cord in laminae IV and V, but particularly at the border between these laminae. Most were in the caudal half of the fourth lumbar segment (L4), caudal to Clarke's column. However, neurones of this type were encountered as far caudal as the middle of the fifth lumbar segment (L5) and as far rostral as the middle of the third lumbar segment (L3). 3. The morphology of the neurones was investigated following intracellular staining with horseradish peroxidase (HRP). Fourteen well-filled cells were recovered. They had large somata and extensive dendritic arborizations within the dorsal horn which could extend more than 2 mm rostro-caudally. The most dense arborization was in laminae III and IV, just dorsal to the cell bodies. 4. The axons of all fourteen cells could be followed well into the white matter. All of them passed into the dorsal part of the ipsilateral lateral funiculus where they ascended. All followed a similar indirect course through the grey matter. Despite careful inspection, initial axon collaterals were never found. 5. All of the neurones were antidromically activated by low-intensity electrical stimulation of the dorsolateral part of the ipsilateral lateral funiculus in the thoracic region and from the cerebellum. The conduction velocities of the axons ranged from 62 to 112 m s-1 (mean 84.2 (S.D. +/- 10.1) m s-1). 6. The axonal terminations of some neurones were investigated by mapping the most effective locations for antidromic activation from the cerebellar cortex. Most neurones were activated with lowest stimulus intensities from the rostral part of the anterior lobe. A second effective area was found in the posterior lobe, deep to the paramedian lobule. The majority of neurones were activated from both locations, suggesting that their axons branched to terminate in both areas. 7. On the basis of their projection and termination, it is proposed that the axons of these dorsal horn spinocerebellar tract neurones contribute to the dorsal spinocerebellar tract (DSCT).

Action Potentials↗
PubMedDate not supplied

Cognitive impairment and central motor conduction time in chronic alcoholics.

The non-invasive technique of transcranial magnetic stimulation (TMS) was used in 62 chronic alcoholics to assess the functional status of descending motor pathways. The main aims of this study were: to investigate asymptomatic upper motor neuron dysfunction in alcoholics as well as to assess its relationship with parameters reflecting the intensity of exposure to alcohol; and to evaluate a possible relationship between central motor conduction time (CMCT) prolongation and neuropsychological measures of alcohol-related brain damage. Compared to control subjects, chronic alcoholics exhibited a significant prolongation of CMCT (23 out of 62 subjects). No significant correlation was found between CMCT prolongation and intensity and duration of abuse, presence of peripheral neuropathy, or brain atrophy on CT scans. Prolongation of CMCT from the upper limb correlated significantly with impairment of frontal skills on neuropsychological testing (p<0.01). These findings suggest that TMS may be a sensitive method for the detection in alcoholics of subtle neurological dysfunction, not confined to motor pathways.

Adult↗
PubMed2004

An FPGA-based approach to high-speed simulation of conductance-based neuron models.

The constant requirement for greater performance in neural model simulation has created the need for high-speed simulation platforms. We present a generalized, scalable field programmable gate array (FPGA)-based architecture for fast computation of neural models and focus on the steps involved in implementing a single-compartment and a two-compartment neuron model. Based on timing tests, it is shown that FPGAs can outperform traditional desktop computers in simulating these fairly simple models and would most likely provide even larger performance gains over computers in simulating more complex models. The potential of this method for improving neural modeling and dynamic clamping is discussed. In particular, it is believed that this approach could greatly speed up simulations of both highly complex single neuron models and networks of neurons. Additionally, our design is particularly well suited to automated parameter searches for tuning model behavior and to real-time simulation.

Animals↗
PubMed1983

Splanchnic afferent input to the lateral reticular nucleus of the cat.

The afferent input from splanchnic nerves to the lateral reticular nucleus (LRN) was studied in anesthetized cats. The activity of neurons of the parvi- and magnocellular regions of the nucleus was recorded by means of extracellular microelectrodes. The LRN neurons were stereotaxically located and identified by their response to antidromic stimulation of the cerebellar cortex. Activity of the LRN neurons studied was modified by electrical stimulation of the ipsi- and contralateral splanchnic nerves, and by mechanical stimulation of peritoneal receptors. Response latencies to stimulation of the splanchnic nerves were measured, and conduction velocities of peripheral fibers were determined; most of them were myelinated fibers with a small diameter (sub-groups of A- A gamma delta) and were connected with 'peritoneal movement mechanoreceptors'. Numerous convergences were observed. All of the tested neurons which responded to stimulation of the homolateral splanchnic nerve also responded to stimulation of the contralateral splanchnic and to diverse somatic stimulations. In 90% of the neurons tested, a splanchno-cortical convergence (sensory-somatic cortex) was observed. Two possible roles of splanchnic afferents that activate neurons of the LRN were considered: (1) they might, like other spinal inputs, influence LRN and cerebellar control of motor activity; and (2) they might also participate in cardiovascular regulations in which the LRN is involved.

Animals↗
PubMed1975

Brain stem reticular units: some properties of the course and origin of the ascending trajectory.

Experiments were conducted in acutely prepared cats anesthetized with halothane-nitrous oxide. Single units were recorded in the mesencephalic and rostral rhombencephalic reticular core, and their ascending axons were stimulated in the mesencephalon, diencephalon, and telencephalon. The locations of stimulation and recording sites were determined by histological examination of the brains. Antidromic spikes were elicited by electrodes with a stimulus spread of approximately 300 mum and were collided with spontaneous (orthodromic) spikes to confirm antidromicity. Projecting axons were found to be scattered diffusely in the central mesencephalon in both the tegmentum and tectum. At the mesodiencephalic junction, the dorsal extent of the pathway lay in the posterior commissure and the ventral extent in the substantia nigra. More rostrally, a ventral group of axons was found in or near the supraoptic nucleus in the hypothalamus, and near the floor of the forebrain in the basal telencephalon. In agreement with previous reports, a dorsal component was located in the medial thalamus, most often in the nucleus centralis lateralis. The conduction velocity of each axon was determined, and they suggest a wide range of axon size in the ascending pathways. There may be a slight predominance of smaller fibers in the dorsal component and of larger fibers in the ventral component; however, all parts of the pathways were relatively heterogenous. The units from which projecting axons arose were found in the rostral rhombencephalon, and no units sending their axons along the restricted pathways investigated were identified rostral or caudal to this region. However, no conclusion is drawn concerning units within the region extending from 0.0 to 0.6 mm of the midline or other brain stem regions known to be monoamine-rich and to have ascending axons; these cellular populations were not examined.

Anesthesia, Inhalation↗
PubMed2001

Neurotoxic effects of fifth-generation dentin adhesives on rat sciatic nerve.

This study evaluated the effect of the fifth-generation dentin adhesives, Single Bond (SB), Excite (EX), Prime & Bond NT (PB), and Optibond Solo (OS) on nerve conduction. Isolated rat sciatic nerves were placed between two suction electrodes in a bath containing tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials (cAPs) were recorded before and after contact with the materials. SB, EX, and PB caused total inhibition of the cAPs, with PB being the fastest (73 +/- 5.8 min). All cAPs except one in the PB group were irreversibly inhibited in the SB, EX, and PB groups. As for OS the reduction in cAP was not 50% after an application time of 200 min. Recovery of the cAPs in this group was recorded in an average time of 35 min.

Action Potentials↗
PubMed1994

Effects of preoptic warming on subretrofacial and cutaneous vasoconstrictor neurons in anaesthetized cats.

1. Sympathetic and subretrofacial neuron responses to preoptic warming were studied in chloralose- or Saffan-anaesthetized, paralysed cats. 2. Warming a thermode in the preoptic region inhibited the activity of cutaneous vasoconstrictor fibres supplying hairy skin. Muscle vasoconstrictor fibre activity recorded at the same time was either unaffected or raised. 3. Small injections of sodium glutamate (5 nl, 0.1 M) were made into the region of the subretrofacial nucleus in the ventrolateral medulla. The part of that region where glutamate injections evoked brisk increases in cutaneous vasoconstrictor fibre activity was chosen for further study. 4. Extracellular single unit recordings were made in that area from seventy-seven subretrofacial neurons, which were identified by their barosensitivity (inhibition by carotid blind sac inflation). Forty-seven of them were antidromically activated by stimulation in the spinal cord. 5. The activity of twenty subretrofacial neurons (twelve proven bulbospinal) was significantly reduced by periods of preoptic warming. Cutaneous vasoconstrictor activity recorded at the same time also fell. Forty-nine subretrofacial neurons (thirty-five proven bulbospinal) were unaffected or excited by periods of preoptic warming that inhibited cutaneous vasoconstrictor fibres. The response of eight neurons was unclear. 6. No difference in either mean firing rate or axonal conduction velocity was found between neurons inhibited by preoptic warming and other subretrofacial neurons. 7. The subretrofacial neurons inhibited by warming were found intermingled with those unaffected or excited. Marked recording sites of warm-inhibited neurons were clustered around the ventromedial border of the subretrofacial nucleus. 8. In two cats, bilateral inhibition of subretrofacial neurons by surface application of 1 M glycine reduced cutaneous vasoconstrictor fibre activity to 32 and 44% of control levels. 9. The results suggest that specific cutaneous vasoconstrictor premotor neurons exist in the subretrofacial nucleus. These apparently provide most of the background excitatory drive to cutaneous vasomotor neurons. Central warming stimuli may act, at least in part, by withdrawing that drive.

Anesthesia↗
PubMed1987

The use of local anaesthetic microinjections to identify central pathways: a quantitative evaluation of the time course and extent of the neuronal block.

The time course and extent of local anaesthetic blocks within the spinal cord of cats were evaluated. A monopolar stimulation electrode with the tip lowered into the dorsal columns (DC) 1000 microns below cord surface was used to activate antidromically DC fibers at the T13 level and evoke cord dorsum potentials at the level of the lumbar spinal cord. The amplitude of the negative deflection, the N-wave, was determined for various stimulation intensities (stimulation-response-function, SRF). Lidocaine (1%) was microinjected in volumes of 0.5 or 1.0 microliter into the DC from a glass micropipette 1 mm caudal to the stimulation site. Conduction block was characterized by a reversible shift of the SRFs to higher stimulation intensities. The diameter of the blocked area in the transverse plane was evaluated from threshold intensities and was found to be 0.9 +/- 0.1 mm 4 to 30 min after the injection of 0.5 microliter lidocaine and 1.6 +/- 0.36 mm 10 to 45 min after the injection of 1.0 microliter lidocaine. In the sagittal plane, the diameter of the blocked area following 1.0 microliter lidocaine was found to be up to 2.8 mm. The DC-block was reversible within 92 min following injection of 1.0 microliter and 69 min after the injection of 0.5 microliter lidocaine. The application of the present findings for blocks in other CNS structures is discussed.

Anesthetics, Local↗
PubMed1985

Antidromic activation of dorsal raphe neurons from neostriatum: physiological characterization and effects of terminal autoreceptor activation.

Three types of neurons, distinguished on the basis of their spontaneous firing rates and patterns, extracellularly recorded waveforms and responses to neostriatal stimulation, were observed in the dorsal raphe nucleus in urethane-anesthetized rats. Type 1 neurons (presumed to be serotonergic) fired spontaneously from 0.1 to 3 spikes/s in a regular pattern, with initial positive-going bi- or triphasic action potentials. Type 1 cells exhibited long-latency antidromic responses to neostriatal stimulation (mean +/- S.E.M. 24.9 +/- 0.3 ms) that sometimes occurred at discrete multiple latencies, and supernormal periods persisting up to 100 ms following spontaneous spikes. Type 2 cells fired spontaneously in an irregular, somewhat bursty pattern from 0 to 2 spikes/s with initial negative-going biphasic spikes, and were antidromically activated from neostriatal stimulation at shorter latencies than Type 1 cells (21.8 +/- 0.9 ms). Type 3 cells were characterized by initial positive-going biphasic waveforms and displayed a higher discharge rate (5-30 spikes/s) than Type 1 or Type 2 cells. Type 3 cells could not be antidromically activated from neostriatal stimulation. The relatively long conduction time to neostriatum of the Type 1 presumed serotonergic neuron is discussed with respect to previous interpretations of the synaptic action of serotonin in the neostriatum. In conjunction with these antidromic activation studies, the neurophysiological consequences of serotonergic terminal autoreceptor activation were examined by measuring changes in the excitability of serotonergic terminal fields in the neostriatum following administration of the serotonin autoreceptor agonist, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT). The excitability of serotonergic terminal fields was decreased by intravenous injection of 40 micrograms/kg 5-MeODMT, and by infusion of 10-50 microM 5-MeODMT directly into the neostriatum. These results are interpreted from the perspective of mechanisms underlying autoreceptor-mediated regulation of serotonin release.

Animals↗
PubMed1983

Identification of spinally projecting neurones in the A1 catecholamine cell group of the ventrolateral medulla.

In anaesthetized rats, neurones were found in the ventrolateral medulla that responded to antidromic stimulation of their axons in the thoracic spinal cord. These neurones were identified as being antidromic, according to various established electrophysiological criteria. A total of 44 antidromically identified neurones were found, 23 had conduction velocities below 2.0 m/s. Many (70%) had ongoing activity with a slow firing rate (0.2-5.0 Hz). Catecholamine-containing cells were visualized in this ventrolateral region using a modified Mg+-catalyzed glyoxylic acid technique and revealed multipolar, small diameter cells (17-20 microns) which were diffusely scattered (as demonstrated in previous histofluorescence studies). The Pontamine sky blue-marked recording sites of 7 units (0.3-1.1 m/s) showed close apposition to a CA-fluorescent cell whilst a further 4 (2.0-2.7 m/s) could not be correlated with the presence of a fluorescent cell. The results are discussed in the light of recent data in the rat, suggesting that the spinal cord catecholamine innervation arises from brainstem cell groups other than A1.

Animals↗
PubMed2006

Shunting versus inactivation: simulation of GABAergic inhibition in spider mechanoreceptors suggests that either is sufficient.

Afferent neurons entering the central nervous systems of vertebrates and invertebrates receive presynaptic inhibition on their axon terminals. This usually involves an increase in membrane conductance (shunting) and depolarization (primary afferent depolarization, PAD). In arachnids and crustaceans the peripherally located parts of afferent neurons also receive efferent synapses. GABA (gamma-aminobutyric acid) plays a major role in both central and peripheral inhibition, activating chloride channels that depolarize the membrane and increase its conductance. Although both central and peripheral inhibition have been widely investigated, debate continues about the mechanisms involved, especially concerning the relative contributions of shunting versus inactivation of sodium channels by depolarization. Sensory neurons innervating spider VS-3 slit sensilla are accessible to intracellular recordings during mechanical or electrical stimulation. These neurons are inhibited by GABA, and both the electrophysiology and pharmacology of this inhibition have been studied previously. Here, we developed a Hodgkin-Huxley style model to simulate VS-3 neuron activity before and after GABA treatment. The model indicates that GABA-activated chloride current can entirely account for action potential suppression, and that either shunting or inactivation are sufficient to produce inhibition. This model also demonstrates that slowing of sodium current contributes to inhibition.

Animals↗
PubMed2001

Excitatory and inhibitory mechanisms in Wilson's disease: investigation with magnetic motor cortex stimulation.

We have evaluated cortical excitability in nine patients affected by Wilson's disease (WD) using transcranial magnetic (TMS) and electric (TES) cortical stimulation and central silent period (CSP) data. A clinical score was derived from the sum of scores assigned to extrapyramidal, pyramidal and cerebellar signs. All patients underwent TMS. Motor evoked potentials (MEPs) from abductor pollicis brevis (APB) and tibialis anterior (TA) muscles were recorded. MEP threshold and amplitude, central motor conduction time (CMCT), CSP threshold, CSP and peripheral silent period (PSP) duration were measured. Three patients also underwent transcranial bifocal electric cortical stimulation (TES) and MEPs were recorded from the APB muscle, and CMCT, MEP threshold and amplitude were measured. TMS MEPs were absent from relaxed muscles in six patients and from contracted muscles in three. CMCT was prolonged in six patients. APB CMCT correlated with clinical score. In three patients in whom TMS revealed abnormal or no MEP, TES MEPs were of normal threshold and amplitude. The CSP threshold was increased in seven patients, and CSP was absent in one. These results suggest an intracortical presynaptic motor dysfunction in WD.

Adult↗
PubMed1990

Functional connections in the human temporal lobe. I. Analysis of limbic system pathways using neuronal responses evoked by electrical stimulation.

Connections in the human mesial temporal lobe were investigated using brief, single pulses of electrical stimulation to evoke field potential responses in limbic structures of 74 epileptic patients. Eight specific areas within these structures were stereotactically targeted for study, including amygdala, entorhinal cortex, presubiculum, the anterior, middle and posterior levels of hippocampus and the middle and posterior levels of parahippocampal gyrus. These sites were studied systematically in order to quantitatively assess the response characteristics and reliability of responses evoked during stimulation of pathways connecting the areas. Specific measures included response probability, amplitude, latency and conduction velocities. The results are assumed to be representative of typical human limbic pathways since all recordings were made interictally and response probabilities across sites were not found to differ significantly between non-epileptogenic vs. identified epileptogenic regions. Field potentials ranging in amplitude from less than 0.1 to greater than 6.0 mV were evoked ipsilaterally, with mean onset latencies and conduction velocities ranging from 4.4 ms and 3.64 m/s in the perforant pathway connecting entorhinal cortex to anterior hippocampus to 24.8 ms and 0.88 m/s in the pathway connecting the amygdala and middle hippocampus. Stimulation of presubiculum and entorhinal cortex were most effective in evoking widespread responses in adjacent limbic recording sites, whereas posterior parahippocampal gyrus appeared functionally separated from other limbic sites since its probability of influencing ipsilateral sites was significantly lower than any other area. It was particularly noteworthy that stimulation did not evoke responses in any sites in contralateral hippocampal formation; even though a large number of sites were tested with bilateral implantation of homotopic electrodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗