Retinal prosthetic devices are being developed to bypass degenerated retinal photoreceptors by directly activating retinal neurons with electrical stimulation. However, the retinal circuitry that is activated by epiretinal stimulation is not well characterized. Whole-cell patch clamp recordings were obtained from ganglion cells in normal and rd mice using flat-mount and retinal slice preparations. A stimulating electrode was positioned along the ganglion cell side of the preparation at different distances from the stimulated tissue. Pulses of cathodic current evoked action potentials in ganglion cells and less frequently evoked sustained inward currents that appeared synaptic in origin. Sustained currents reversed around ECl and were inhibited by blockade of α-amino-3-hydroxyl-5-methyl-4-isoxazole-proprionate (AMPA)-type glutamate receptors with 2,3-dihydroxy-6-nitro-sulfamoyl-benzo(f)-quinoxaline-2,3-dione (NBQX), γ aminobutyric acid a/c (GABAa/c) receptors with picrotoxinin, or glycine receptors with strychnine. This suggests that epiretinal stimulation activates glutamate release from bipolar cell terminals, which in turn evokes release of GABA and glycine from amacrine cells. Synaptic current thresholds were lower in ON ganglion cells than OFF cells, but the modest difference did not attain statistical significance. Synaptic currents were rarely observed in rd mice lacking photoreceptors compared to normal retina. In addition, confocal calcium imaging experiments in normal mice retina slices revealed that epiretinal stimulation evoked calcium increases in the outer plexiform layer. These results imply a contribution from photoreceptor inputs to the synaptic currents observed in ganglion cells. The paucity of synaptic responses in rd mice retina slices suggests that it is better to target retinal ganglion cells directly rather than to attempt to engage the inner retinal circuitry.

The poultry industry has seen significant changes in the methods used to harvest fresh poultry meat over the past four decades. Some of the major changes include a more than four-fold increase in line speed (new plants are designed to process 12,000 broilers per hour), a large increase in the proportion of cut up and deboned meat produced, as well as substantial improvements in sanitation. These advancements have been possible by gaining knowledge in areas such as computer science (e.g. image analysis, on line weighing and tracking), live bird handling (transportation, unloading, stunning), muscle biology (post mortem processes), heat and mass transfer (scalding, chilling), and engineering (machine building, metallurgy). This article includes a general overview of the different steps involved in primary poultry processing and focuses on some of the principles that have been used to achieve greater efficiencies in mechanising the whole process. The focus areas include stunning, electrical stimulation, chilling, and mechanical filleting. These topics will be used to demonstrate the importance of obtaining high meat quality (e.g. fewer downgrades, high water holding, acceptable tenderness and colour) currently demanded by processors as well as consumers. The advantages of in-line-processing will also be highlighted, where improved efficiencies have been achieved by incorporating real-time computerised monitoring and tracking systems.

Overall, a comprehensive understanding of the whole process and the integration of the different steps is a challenge that must be met by both the equipment manufacturer and processing plant personnel. Because of the increased complexity of the whole integrated process, it is highly recommended that the processor team up with a very knowledgeable equipment manufacturer who has the technical understanding and experience within all stages of the process (farm gate to fork), to effectively optimise quality, yield, and speed.

In a series of physiological experiments, a total of 203 neurons at the Area 17/18 border were recorded with a callosal link either demonstrated by antidromic or transsynaptic activation from stimulating electrodes located in the homotopic contralateral hemisphere (CH), or in the splenial segment of the corpus callosum (CC). Forty-four percent of the transcallosal cells could also be driven from stimulating electrodes in or just above the lateral geniculate nucleus (OR1). The majority (69%) of transcallosal neurons were classifiable as belonging to the complex family (B and C cells) and most of these were found in the supragranular laminae and in lamina 4A. The ocular dominance distribution of transcallosal cells was trimodal, consisting of roughly equal numbers of monocularly dominated and binocularly balanced neurons. Estimates of conduction time and synaptic delay were obtained for neurons driven from CH, CC, and from OR1, and in most instances the response latency was short enough to suggest a monosynaptic input from either the ipsi- or contra-lateral hemisphere. The distribution of transcallosal conduction times showed that S cells, as a class, had significantly faster conduction than cells of the complex family but otherwise there was no obvious signs of multimodality in the distribution curve. An analysis of the synaptic delays in transcallosal activation produced a mean of 0.6 to 0.7 ms but some were too short to be consistent with a transsynaptic drive, suggesting that some cells with an antidromic drive may have been included in the transsynaptic category. Results are interpreted in terms of the contribution made by the corpus callosum to stereoscopic vision.

Postsynaptic responses of tectal cells in the bullfrog (Rana catesbeiana) were intracellularly recorded following electrical stimulation of the optic tract and the nucleus isthmi, and fluorescent dye, Lucifer yellow, was injected into some of the impaled cells to show their morphologies. Two main response types were found: The first type was an EPSP followed by an IPSP, and the second type was single IPSP. The first type predominates in cells responding to the optic tract stimulation and the second type prevails in cells responding to the isthmic stimulation. Fifteen cells stained with Lucifer yellow were localized in layer 6 (11 cells), layer 7 (1 cell), and layer 8 (3 cells). They were mainly identified as pear-shaped cells, large ganglionic cells, and stellate cells. Three injections demonstrated “dye-coupling,” which labeled up to six cells following one injection. Comparisons of postsynaptic potentials with cellular morphologies suggested that the nucleus isthmi could directly excite large ganglionic neurons in layer 6. Synaptic mechanisms for strong isthmic inhibition on the tectal neurons remain unknown.

In this study, we examined procedures that alter saccadic latencies and target selection to visual stimuli and electrical stimulation of area V1 in the monkey. It has been shown that saccadic eye movement latencies to singly presented visual targets form a bimodal distribution when the fixation spot is turned off a number of milliseconds prior to the appearance of the target (the gap period); the first mode has been termed express saccades and the second regular saccades. When the termination of the fixation spot is coincident with the appearance of the target (0 ms gap), express saccades are rarely generated. We show here that a bimodal distribution of saccadic latencies can also be obtained when an array of visual stimuli is presented prior to the appearance of the visual target, provided the elements of the array overlap spatially with the visual target. The overall latency of the saccadic eye movements elicited by electrical stimulation of area V1 is significantly shortened both when a gap is introduced between the termination of the fixation spot and the stimulation and when an array is presented. However, under these conditions, the distribution of saccadic latencies is unimodal. When two visual targets are presented after the fixation spot, introducing a gap has no effect on which target is chosen. By contrast, when electrical stimulation is paired with a visual target, introducing a gap greatly increases the frequency with which the electrical stimulation site is chosen.

A series of 49 cases with difficult to control seizures and non-candidates for ablation of the epileptic focus has been treated with electrical stimulation of the centromedian thalamic nuclei (ESCM).

Selected cases were: (1) epilepsia partialis continua (EPC) (n = 5); (2) partial complex seizures (n = 16); (3) bilateral frontal parasagittal seizures (n = 6); (4) Lennox-Gastaut syndrome (n = 22). All patients had four contact electrodes placed bilaterally through frontal parasagittal burr holes and guided by ventriculograms. Plotting of electrodes on sagittal and frontal sections of the Schaltenbrand and Bailey’s atlas permitted to determine their location. Electrodes were left externalized for periods of weeks to months to carry out the following tests. (1) Recordings of spontaneous seizures occurring during wakefulness and sleep. (2) Electrophysiological confirmation of their position by means of recruiting responses and desynchronization induced by low and high frequency stimulation. (3) Effects of high frequency stimulation on interictal and ictal activities. Electrodes were internalized and connected to a subcutaneous pulse generator programmed for alternating right and left ESCM 1 min ON and 4 min OFF at 60–130 Hz, 0.21–0.45 ms, 3–5 V forward and backward for 24 h per day. Repeated EEG recordings and a calendar of seizures were used for follow-up from 1 to 9 years.

CM paroxysmal discharges followed the initiation of seizures in cortical areas, occurred simultaneously with spike wave (SKW) complexes in cortical areas in Lennox-Gastaut syndrome and preceded the initiation of cortical SKW and clinical seizures in typical absences. Low frequency stimulation (6–8 cps) induced recruiting responses that were associated with those electrodes that produced best seizure control. Good to excellent results were obtained in cases of EPC and Lennox-Gastaut syndrome and on generalized tonic clonic convulsions (GTCs) and atypical absences (AA) with tonic or clonic components.

Consequently, we came to the conclusions that the CM participates in the propagation of most seizure types and also in the genesis of some of them and that ESCM is a safe and useful alternative for the treatment of some of the most difficult cases of uncontrollable seizures.

Advances in the neurosciences and functional neurosurgery have led to a renaissance in the use of brain stimulation technology. A number of intractable neurological disorders can now be safely and successfully treated with brain stimulation. Although this technique was first performed over 50 years ago, it has only now begun to reach its vast clinical potential. This article will provide a historical overview of brain stimulation, describe state-of-the-art clinical applications, and discuss future prospects in this rapidly advancing field.

High-frequency electrical stimulation (deep brain stimulation (DBS)) of the thalamus and basal ganglia (subthalamic nucleus, internal segment of the globus pallidus) is used to treat motor disorders arising in Parkinson’s disease, multiple sclerosis, and essential tremor. Although clinically effective, the mechanisms of action of DBS are unknown. A number of plausible hypotheses have been offered, however, until the effects of the applied current on the surrounding neurons are understood, it will prove difficult to determine the underlying mechanisms. Computational models of central neurons were used to determine what neural elements are activated by extracellular stimulation. Thresholds for activation of local cells and axons of passage were similar with conventional stimuli. With electrodes positioned over the cell body, action potential initiation invariably occurred in the axon. As a result, activity generated by extracellular stimulation could vary between the soma and axon of the same neuron. Additionally, extracellular chronaxie times were insensitive to the neural element (cell versus axon) that was stimulated. The non-specific activation that occurs with conventional stimuli complicates the determination of the mechanisms of action and may contribute to side effects. Novel asymmetrical stimuli were developed that enable selective stimulation of different populations of neural elements. Understanding the effects of extracellular stimulation on central neurons will limit the plausible hypotheses to explain the effects of DBS, and lead to new stimulation technologies that will improve clinical efficacy.

We analyzed postsynaptic potentials and dye-labeled morphology of tectal neurons responding to electrical stimulation of the optic nerve and of the nucleus isthmi in a reptile, Gekko gekko, in order to compare with previously reported interactions between the optic tectum and the nucleus isthmi in amphibians and birds. The results indicate that isthmic stimulation exerts inhibitory and excitatory actions on tectal cells, similar to dual isthmotectal actions in amphibians. It appears that dual actions of the isthmotectal pathway in amphibians and reptiles are shared by two subdivisions of the nucleus isthmi in birds. The morphology of tectal cells responding to isthmic stimulation is generally similar to that of tectoisthmic projecting neurons, but they differ particularly in that some tectoisthmic cells bear numerous varicosities whereas cells receiving isthmic afferents do not. Thus, it is likely that at least some tectoisthmic cells may not be in the population of tectal cells that can be affected by isthmic stimulation. Forty-four percent of injections resulted in dye-coupled labeling, suggesting extensive electrical connections between tectal cells in reptiles.

A case is reported in which a Nucleus 22 channel intracochlear implant was used to treat a deaf Hungarian woman (aged 37 years) with a 34-year history of grand mal (GM) epilepsy maintained on carbamazepinediazepam combination therapy who had not benefited from conventional hearing aids. Pre-operative electrical stimulation of the acoustic nerve, however, exhibited a good nerve function with no evidence of abnormal waveforms in the electroencephalogram (EEG). Successful intracochlear insertion of the 22 electrode resulted in a 40 dB hearing improvement at frequencies 250–2000 Hz in the implanted ear with no signs of pathologic wave activity at either the previously recognized epileptic focus (fronto-precentral region) or indeed, in other regions of the brain at use of the implant. We conclude that intracochlear implantation per se is not a hazardous intervention in patients with fronto-precentral epileptic foci.

The effect of electrical stimulation on the quality of P. setiferus sperm cells was studied during the regeneration of the spermatophore. The proportion of the animals that responded to electroejaculation was quantified and the number of live, abnormal and dead cells, as well as the relationship between the number of cells and body weight, were taken into consideration as indicators of the effect of manipulation during stimulation. It was found that electrical stimulation caused some degree of spermatophore expulsion in 78% of the cases. Total expulsion of the spermatophores occurred in only 8.3% of the cases. A logistic curve was adjusted to the relationship between the number of sperm cells and the weight of the shrimp. After regeneration no curve was adjusted to the relationship. Eighty per cent of the stimulated shrimp regenerated the spermatophore in a maximum of 168 h. Fifty per cent regeneration was obtained in 96 h after stimulation. A decrease in the number of live cells from 26.8 to 7.6 million and an increase in abnormal (from 0.02 to 3.92 million) and dead (from no cells dead to 4.6 million) respectively, were registered for regenerated animals. Necrotic areas in 60% of the ampulae of regenerated shrimps were also observed. Bacteria associated with the necrotic ampulae was observed when counting sperm. As the spermatophore of this species is complex, it is necessary to search for a way to reduce the stress produced by the handling of the ampulae so as to avoid altering the reproductive capacity of the shrimp.

Computerized tomographic procedures have been used extensively since their introduction to examine specific language disabilities in aphasic patients and to correlate anatomical and clinical changes. The resulting overwhelming evidence in favour of lateralisation and localisation has been confirmed by regional blood flow studies and punctate electrical stimulation as well as by the topographic maps provided by neurometries. That specific lexical functions are localised within the peri-Sylvian cortex in the left cerebral hemisphere is now generally accepted, but the macroscopic mapping, which largely ignores the contribution of the ipsilateral thalamus and possibly of the basal nuclei, must not be mistaken for the language encoding processes in the parallel pathways which have been identified.