Attila Tóth

Improved version of the printed circuit board (PCB) modular multi-channel microdrive for extracellular electrophysiological recordings

The modular multi-channel PCB microdrive was described some years ago, since then several improvements were introduced while using these drives. Utilizing several years of experience with the original PCB microdrive we redesigned it to improve its stability and usability. The application of the printed circuit board technology and the extensive use of flexible fused silica capillaries for fabrication of the microdrive are described in detail. The improved design led to a low cost and light-weight multi-channel microdrive with outstanding modularity for extracellular field, single unit or multiunit tetrode recording up to 64/128 channels.

Responses of rat medial prefrontal cortical neurons to Pavlovian conditioned stimuli and to delivery of appetitive reward

In the present experiments, medial prefrontal cortical (mPFC) neurons were extracellularly recorded by means of tetrode electrodes to examine their possible role in the prediction of appetitive reward. Two different cue tones (CS) and sucrose solution or water reward (US) were associated in a Pavlovian conditioning paradigm. In order to test behavioral correlate of the CS-US association, the head acceleration before the first lick of licking cluster was measured. Neuronal activity changes in the mPFC were analyzed (i) during the CS presentations; (ii) before the first lick of licking clusters; (iii) during consummation; and (iv) we also examined whether consummation was represented in neurons responding to the CSs. There was a difference between the head accelerations to the different USs during early or late occurring first approaches, but there was no such a difference during intercluster approaches. A significant proportion of neurons changed their firing rate during the CS presentation, before the first lick of licking cluster or during licking of the reward. Both, excitatory and inhibitory responses were observed. A subpopulation of neurons responding to the CSs also responded during reward consumption. Differential population activities of excitatory neurons were recorded in response to the different CSs, CS evoked approach behaviors and consumption of different rewards. Neuronal responses also discriminated among the CSs and trials with or without consummation. These results provided evidence for the involvement of mPFC neurons in the prediction, representation and organization of conditioned behavioral actions, such as approaches to rewards and consummation.

The application of cross-point switch arrays as input selector switch devices for multi-channel electrophysiological experiments

Integrated circuits (ICs) containing cross-point switch arrays were applied to create analog input selector switch devices for multi-channel electrophysiological experiments. The described analog input selector switch devices make it possible to connect to the main amplifiers inputs those microelectrode and preamplifier output wires that yield unit discharges of acceptable shape and amplitude, or yield other kind of acceptable electrophysiological signals (EEG, EP). This kind of selector allows to use higher number of preamplifier channels and to ignore the input channels without adequate signals or the channels with noisy inputs. No manual switching is required, as the work is done by computer controlled switches. The switch positions can be saved and reloaded at the next experimental session through an I/O port (e.g. the parallel port) of the computer.

Implementation of a galvanically isolated low-noise power supply board for multi-channel headstage preamplifiers

Custom made multi-channel headstage preamplifiers are traditionally powered by battery. By the use of an isolated unregulated DC/DC converter integrated circuit (DCP010512B from Texas Instruments Inc., TX, USA), here we describe the implementation of a galvanically isolated low-noise power supply board for multi-channel headstage preamplifiers. The implemented galvanically isolated power supply board provides the same quality noise free recording as the battery power supply. The non-isolated part of the power supply board is powered by standard 230 V AC/6 V DC wall mount adapter or USB cable. The described galvanically isolated power supply board can replace the batteries in preamplifier power supplies without any deterioration of the quality of recordings.

The MAM-E17 schizophrenia rat model: Comprehensive behavioral analysis of pre-pubertal, pubertal and adult rats

&NA; The MAM‐E17 model is one of the most accepted schizophrenia rat models, which follows the neurodevelopmental theory of the disease. While symptoms of MAM‐E17 rats were studied extensively, their examinations were usually restricted to adulthood and in a few cases to prepuberty. It is well known, however, that schizophrenia symptoms often start at puberty or early adulthood. Therefore the purpose of this study was to investigate the behavioral characteristics of MAM‐E17 rats in various tests throughout three different age‐periods, namely in prepuberty, late puberty and adulthood. In open field test, MAM‐E17 rats displayed increased locomotor activity, elevated sniffing frequency and, as tendency, enhanced rearing activity. The elevated activity turned up in late puberty and remained there in adulthood, too. There was also a deficient prepulse inhibition (PPI) of startle response in late puberty and adulthood, but not before puberty. In rotarod task, MAM‐treated rats performed better than control rats. The enhanced performance on rotarod was only present in late puberty and adulthood. In elevated plus maze test MAM‐treated rats displayed diminished anxiety mostly in prepuberty. Histological analysis revealed reduced volume and cell disarray in the dorsal hippocampus. This is the first comprehensive study about symptoms of MAM‐E17 rats manifested in behavioral tests carried out in prepuberty, late puberty and adulthood. Results display the age‐dependent appearance of schizophrenia symptoms in the same rats. The present findings provide basic information to accomplish the schizophrenia related animal research, as well as can also confer further data to develop preventive treatment for human patients.

Implementation of a miniature sized, battery powered electrophysiological signal-generator for testing multi-channel recording equipments.

Testing electrophysiological recording equipments is an important task in multi-channel extracellular in vivo electrophysiology. In this paper, a miniature, battery powered multi-channel electrophysiological signal-generator (ESG) is described that was designed for this purpose. The device is based on a Xilinx CPLD (Complex Programmable Logic Device) and it is powered by a 3V lithium coin battery. It is a useful tool for calibration and testing the performance, quality and parameters of the recording equipments used for acquiring EEG, field potentials, ECG, EMG, and multiple unit activity. The device is ideally suited to identify instances when errors interfere with the proper recording, and repair of wiring or service of the equipment is needed. Two versions of the device are described; one is for 16 (ESG16), and another is for 32 channels (ESG32). Both versions provide amplitude and time calibration, as well as cross-talk and CMRR (common mode rejection ratio) testing for the recording equipment.

Neuronal coding of auditory sensorimotor gating in medial prefrontal cortex

Abstract The medial prefrontal cortex (mPFC) is thought to be an essential brain region for sensorimotor gating. The exact neuronal mechanisms, however, have not been extensively investigated yet by delicate single unit recording methods Prepulse inhibition (PPI) of the startle response is a broadly used important tool to investigate the inhibitory processes of sensorimotor gating. The present study was designed to examine the neuronal mechanisms of sensorimotor gating in the mPFC in freely moving rats. In these experiments, the animals were subjected to both pulse alone and prepulse + pulse stimulations. Head acceleration and the neuronal activity of the mPFC were simultaneously recorded. To adequately measure the startle reflex, a new headstage with 3D‐accelerometer was created. The duration of head acceleration was longer in pulse alone trials than in prepulse + pulse trial conditions, and the amplitude of head movements was significantly larger during the pulse alone than during the prepulse + pulse situations. Single unit activities in the mPFC were recorded by means of chronically implanted tetrodes during acoustic stimulation evoked startle response and PPI. High proportion of medial prefrontal cortical neurons responded to these stimulations by characteristic firing patterns: short duration equal and unequal excitatory, medium duration excitatory, and long duration excitatory and inhibitory responses were recorded. The present findings, first time in the literature, demonstrated the startle and PPI elicited neuronal activity changes of the mPFC, and thus, provided evidence for a key role of this limbic forebrain area in sensorimotor gating process.

Destruction of noradrenergic terminals increases dopamine concentration and reduces dopamine metabolism in the medial prefrontal cortex

HighlightsLesion of noradrenaline terminals in the medial prefrontal cortex was performed.Lesion of noradrenaline terminals decreased noradrenaline concentration.Lesion of noradrenaline terminals increased tissue dopamine concentration.Enhanced dopamine and decreased DOPAC levels were detected by microdialysis.Yohimbine increased noradrenaline, dopamine, but not DOPAC level after the lesion. ABSTRACT Effects of destroyed noradrenergic (NE) innervation in the medial prefrontal cortex (mPFC) were examined on dopamine (DA) content and metabolism. Six‐hydroxy‐DOPA (6‐OHDOPA) or 6‐hydroxy‐dopamine (6‐OHDA) in combination with a potent DA reuptake inhibitor GBR 12935 or 6‐OHDA were injected bilaterally into the mPFC in separate groups of animals. In addition, GBR 12935 or vehicle was injected into the mPFC in two other groups of animals as control experiments. NE and DA concentrations from postmortem tissue of the mPFC were measured using HPLC with electrochemical detection. In addition, extracellular NE, DA and DOPAC levels were determined using in vivo microdialysis after the 6‐OHDA lesion in combination with GBR 12935 pretreatment in the mPFC. Using reverse microdialysis of alpha‐2‐adrenoreceptor antagonist yohimbine, we tested the remaining activity of NE innervation and the extracellular concentration of DA and DOPAC. NE and DA concentrations from postmortem tissue of the mPFC showed that 6‐OHDOPA lesion reduced NE concentration to 76%, which was a non‐significant alteration, however it enhanced significantly DA concentration to 186% compared to vehicle. After 6‐OHDA lesion with GBR 12935 pretreatment, concentration of NE significantly decreased to 51% and DA level increased to 180%. 6‐OHDA lesion without GBR 12635 pretreatment decreased NE concentration to 23% and DA concentration to 67%. In the microdialysis experiment, after 6‐OHDA lesion with GBR 12935 pretreatment, extracellular NE levels were not detectable, whereas extracellular DA levels were increased and DOPAC levels were decreased compared to controls. Reverse microdialysis of yohimbine demonstrated that the residual NE innervation was able to increase NE level and DA levels, but DOPAC concentration remained low after lesion of the NE terminals. These findings suggest that the damage of NE innervation in the mPFC may alter extracellular DA level due to a reduced DA clearance.