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Biomedical subjects

B D Burns

Publications and source records attributed to B D Burns.

At least 19 recordsLinked to original sources
PubMed2001

Low-threshold N-methyl-D-aspartate receptor function correlates negatively with learning.

The intermediate, medial hyperstriatum ventrale (IMHV) is an area of the forebrain of the domestic chick which exhibits great plasticity. Moreover, there is a strong link between plasticity in the IMHV and specific changes in behaviour. The IMHV in vitro is still plastic, and many of its physiological properties are age-dependent, peaking in slices taken from 3- or 4-day-old birds. This 'window' coincides with an important transitional period in a chick's normal behavioural development. It has also been claimed that reversal training is at its most effective in 3- and 4-day-old birds - a proposition which was confirmed by the experiments reported here. A combination of in vivo training followed by in vitro electrophysiology also revealed that the function of low-threshold N-methyl-D-aspartate receptors (one of the age-related variables) is negatively related to the effectiveness of reversal training, when age is held constant.

Age Factors↗
PubMed2000

Effects of nitric oxide release in an area of the chick forebrain which is essential for early learning.

Extracellular recording techniques were used to study the effects of the nitric oxide releasing agents diethylamine-NO (DEA-NO) and S-nitroso-N-acetyl-penicillamine (SNAP) on synaptic transmission in the intermediate and medial part of the hyperstriatum ventrale (IMHV), a part of the domestic chick forebrain that is essential for some forms of early learning. The field response evoked by local electrical stimulation was recorded in the IMHV in an in vitro slice preparation. DEA-NO (100-200 mgr) significantly depressed the field response in a concentration dependent and reversible manner. However, the depression produced by perfusion with 400 mgr DEA-NO, was not reversed following washout of the drug. With 400 mgr DEA-NO, NO reaches a maximum concentration of 10 mgr at 2 min of perfusion, and then declines slowly. SNAP (400 mgr) produced an effect similar to 400 mgr DEA-NO. Neither the immediate nor the longer-term depressive effect of NO is mediated by activation of guanylyl cyclase because in the presence of both low and high doses of ODQ, a potent and selective inhibitor of NO-stimulated guanylyl cyclase, NO produced the same depression of the field response. There is evidence however that the IMHV possesses c-GMP responsive elements since direct perfusion of 8-Br-cGMP (1 mM) produced a long-term but not an immediate depression. The long-term depression produced by 400 mgr DEA-NO was eliminated in the presence of either a selective adenosine A(1) receptor antagonist or an ADP-ribosyltransferase inhibitor. It was also possible to prevent the long-term effect in the presence of tetraethyl ammonium a K(+)-channel blocker. These results suggest that the NO may be acting presynaptically in a synergistic fashion with the adenosine A(1) receptor to depress transmitter release.

Animals↗
PubMed1996

Morphological and electrophysiological properties of neurons in an area of the chick brain involved in learning.

The intermediate, medial part of the hyperstriatum ventrale (IMHV) is an area of the avian forebrain which is essential for two forms of early learning in the domestic chick. We have developed an in vitro slice preparation which contains part of the IMHV and have found that the electrophysiological properties of the area show a considerable degree of plasticity. In particular, age and prior learning appear to modify the properties of single neurons recorded intracellularly. We have used the in vitro slice preparation to make intracellular recordings from 38 single neurons in the IMHV and have then dye-injected each cell to find out whether there is any relationship between electrophysiological and morphological characteristics. The basic membrane properties of each neuron were measured. Responses to standard electrical stimuli, delivered extracellularly, were also recorded, and each neuron was classified on this basis. Finally, the presence or absence of spontaneously occurring bursts of EPSPs was noted. At the end of recording biocytin was injected into the cell. After the tissue had been processed, each cell was drawn. The area of the cell body was measured, the number of dendrites was counted, and dendritic extent and branching were estimated. Each cell was also classified as 'spiny' or 'non-spiny'. We found that neurons displaying one particular type of response to external stimulation possessed a well defined set of morphological and electrical properties. In addition, three parameters--electrical resistance, somatic area, and the presence or absence of dendritic spines--were related to specific subsets of anatomical and physiological characteristics. The possible relevance of these findings to the plasticity of the IMHV is discussed.

Animals↗
PubMed1996

Electrophysiological correlates of prior training: an in vitro study of an area of the avian brain which is essential for early learning.

Day-old domestic chicks will peck at any small, distinct object, such as a metal bead. One-trial passive avoidance learning can be established by coating the metal bead with methyl anthranilate (MeA) and allowing the birds to peck it once, after which they conspicuously avoid it. We have used birds successfully trained not to peck metal beads, and a control set of chicks where the training beads were innocuously dipped in water. Brain slices were prepared from both groups, containing the left, intermediate, medial part of the hyperstriatum ventrale (IMHV)--a region essential for this form of early learning. The electrophysiological properties of neurones in the IMHV were examined in vitro. Neurones recorded intracellularly in slices taken from MeA-trained birds had higher membrane resistances than did cells from water-trained controls. MeA training was also associated with an increased incidence of spontaneous, large EPSPs. Field responses to local electrical stimulation appeared to be somewhat greater in MeA-trained birds than in water-trained controls. In contrast, field potentials proved harder to potentiate with a burst of relatively high frequency stimulation in MeA-trained birds: the change in amplitude was less in MeA-trained birds, and there was less variability than in slices from water-trained controls.

Analysis of Variance↗
PubMed1995

Age and the effects of 2-D,L-amino-5-phosphonovalerate in an area of the chick forebrain which is essential for early learning.

The intermediate, medial part of the hyperstriatum ventrale (IMHV) is a region of the avian forebrain which is known to be essential for early learning in the domestic chick. The IMHV in an in vitro slice preparation displays two forms of synaptic plasticity. The incidence of both varies with age and is maximal between 3 and 5 days post-hatch. Since NMDA receptors are critical for at least one of these plasticities, we have investigated the relationship between age and the contribution of NMDA receptors to the field response evoked by local, low-frequency stimulation and have found that the magnitude of the NMDA-dependent component of the response varies with age peaking between 3 and 5 days post-hatch. Spontaneous neural activity, recorded intracellularly, can be completely and reversibly silenced by NMDA receptor blockade and the incidence of spontaneous activity also varies with age, peaking between 3 and 5 days. These results suggest that the IMHV contains NMDA receptors which can be activated near resting membrane potential. Either the efficiency or the numbers of these receptors is maximal at a specific point in development and their peak activity coincides with a peak in synaptic plasticity. These characteristics are similar to those reported for young mammals.

Age Factors↗
PubMed1995

Noradrenaline and potentiation in the chick brain slice.

The role of the noradrenergic system as a modulator of neurotransmission in the chick forebrain was investigated in brain slices containing the medial hyperstriatum ventrale, an area known to be involved in learning and memory. The alpha 2-agonist clonidine (20 microM) decreased the post-synaptic response to local stimulation at 0.1 Hz, while activation of beta 2 receptors increased this response. Induction of persistent potentiation following stimulation at 5 Hz was blocked by drugs (20 microM ICI 118,551; 20 microM propranolol) which showed preferential antagonistic activity at the beta 2 receptor but not by the beta 1-preferential antagonist timolol. This effect may be due to an interaction with the NMDA receptor system.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1994

Effects of light hatching on synapse number and size in the intermediate and medial part of the hyperstriatum ventrale of the domestic chick.

The effects of pre-hatch light exposure on synaptic development in the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the chick brain were investigated. Quantitative electron microscopical techniques were used to determine the size and numerical density of synapses and it was seen that in light hatched chicks there was a significant increase in the density of synapses in the left IMHV but that the size of synapses in these birds was decreased. These results provide a link between synaptic development and plasticity.

Animals↗
PubMed1993

NMDA-receptors and potentiation in an area of avian brain essential for learning.

The intermediate medial part of the hyperstriatum ventrale (IMHV), part of the avian forebrain, is essential for early learning in the domestic chick. Persistent potentiation (PP) can sometimes be induced in the IMHV in vitro. One can predict success from events which occur during the stimulation (1 min at 5 Hz) which is used for induction: the original response must be transiently replaced by a later, slower response (the LPSR). The LPSR has a comparatively high threshold of activation, its rate of development is inversely related to magnesium concentration and it can be eliminated by NMDA antagonists, as can the induction of PP. PP in the IMHV is therefore dependent upon NMDA receptors and the LPSR represents the activation of these receptors.

Animals↗
PubMed1993

Production of polyrhythms.

Previous research has shown that there are strong constraints on the concurrent performance of nonharmonically related motor sequences such as polyrhythms. A model of polyrhythm production is proposed that involves a hierarchical timing system. The model assumes a single mechanism (a counter) for the timing and serial ordering of responses. Predictions derived from the model were tested in an experiment in which skilled (musically trained) and unskilled Ss attempted to reproduce polyrhythms of varying complexity. The results agreed with the model's predictions and showed that Ss adopted a hierarchical form of integrated motor organization in which movements of the slow hand were subordinate to movements of the fast hand. This strategy was consistent across S groups, polyrhythms, and hand arrangements.

Attention↗
PubMed1992

Morphological correlates of protein kinase C induced potentiation in the chick brain slice.

Continuous perfusion of a chick brain slice with 10 microM 4 beta phorbol 12,13 diacetate (PDAc) produces a significant increase in the amplitude of the response to electrical stimulation at 0.1 Hz recorded within the intermediate and medial part of the hyperstriatum ventrale (IMHV). This PDAc-induced potentiation and that induced by tetanising stimulation appear to share similar mechanisms. Quantitative electron microscopy of synapses within the IMHV from slices in which a PDAc induced potentiation had been produced 30 minutes earlier showed that compared with control slices there was a significant increase in the size of the postsynaptic density of spine synapses. The change was greater in magnitude than that observed in spine synapses following tetanically induced potentiation. No other synaptic parameters were affected.

Animals↗
PubMed1992

Protein kinase activity and synaptic plasticity in a chick brain slice.

In an in vitro slice preparation of the chick brain it is possible to record responses to single electrical stimuli from within the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region known to be involved in learning. The amplitude of such responses is significantly increased by superfusion of the slice with 10 microM 4 beta-phorbol 12,13 diacetate (PDAc), a phorbol ester which stimulates protein kinase activity. The ability of PDAc to induce potentiation is greatest in chicks less than 6 days old. Administration of the kinase antagonist H7 prevents the induction of persistent potentiation and in fact produces a long lasting depression of response amplitude. H7 also produces a short term increase in excitability within the IMHV and results in increased expression of N-methyl-D-aspartate receptor activity.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Potentiation of synaptic responses in slices from the chick forebrain.

Coronal slices, containing part of the medial hyperstriatum ventrale (MHV), were cut from the left forebrains of domestic chicks and maintained in vitro. Records were made of the field responses evoked in the MHV by local electrical stimuli provided at 0.1 Hz. Two 1 min periods of stimulation at 5 Hz, separated by 10 min, were used in attempts to induce a persistent increase in the size of the postsynaptic response to test stimulation at 0.1 Hz. This procedure produced a potentiation which usually lasted longer than 2 h. The probability of inducing this persistent potentiation of the response (PPR) is not distributed evenly over the whole anteroposterior length of the MHV but is higher in slices that also contain the septo-mesencephalic tract ventrally. These are the slices that contain the intermediate part of the medial hyperstriatum ventrale (IMHV); an area that is essential for early behavioural learning. At this level PPR is not confined to the IMHV. It can also be produced in the lateral neostriatum in response to similar local stimulation at 5 Hz. No PPR was observed in either the caudal ectostriatum, or the paleostriatum.

Animals↗
PubMed1991

The effects of age and visual experience on potentiation of responses in slices from the chick forebrain.

A single coronal slice, containing the intermediate part of the medial hyperstriatum ventrale (IMHV) was cut from the left forebrain of a series of domestic chicks and maintained in vitro. Records were made of field responses evoked in the IMHV by local electrical stimuli. Two 1-min periods of 5 Hz stimulation, separated by 10 min, were used in attempts to induce persistent potentiation of the responses (PPR) to test stimulation at 0.1 Hz. In dark-hatched chicks the probability of producing PPR is much higher in slices from chicks aged 2-5 days post-hatch than in those from either younger or older birds. As an independent measure of plasticity in dark-hatched chicks, the probability of eliciting unit responses to repeated stimulation of remote sites in the slice at 3.3 Hz was analysed. This probability was greater in slices from chicks aged 2-5 days than in those from either younger or older birds. In light-hatched chicks the probability of inducing PPR is significantly higher during the first day post-hatch, than in dark-hatched chicks of this age. The probability of producing PPR in slices from light-hatched chicks aged 2-3 days is less than that in slices from either younger or older birds. It is clear that both the age and past experience of the domestic chick affect the neurophysiological properties of slices of brain, tested in vitro.

Age Factors↗
PubMed1991

Morphological correlates of persistent potentiation in the chick brain slice.

In an in-vitro slice preparation of the chick brain it is possible to induce persistent potentiation of responses to single electrical stimuli by giving two bursts of 300 stimuli at 5 Hz separated by ten minutes of control stimulation at 0.1 Hz. We investigated the morphological correlates of this potentiation in a group of 2 day old chicks using quantitative electron microscopical techniques. It was found that in slices which showed a clearly potentiated response there was a significant increase in the size of the postsynaptic densities of synapses on spines in the left hyperstriatum ventrale (IMHV). No such increases were seen in a control group nor in slices which failed to potentiate. These results provide further evidence for the lability of synapses in the IMHV.

Animals↗
PubMed1990

Local circuitry in the IMHV of the domestic chick (Gallus domesticus).

The responses to local stimulation have been recorded from neurons in the intermediate part of the medial hyperstriatum ventrale (IMHV) of the domestic chick, by using an in vitro slice preparation. When the slice is bathed in gassed Krebs' solution, a single stimulus evokes a short-lasting diphasic response. The first phase is negative and lasts some 3 ms, whereas the second, positive phase is often of lower amplitude and usually persists for about 15 ms. The first phase is little altered by perfusion with either Ca2(+)-free Krebs' solution or Krebs' solution containing a high concentration of Mg2+. In contrast, the second phase is abolished by these procedures. The post-synaptic phase is positive when it is recorded anywhere between 0.1-1.25 mm from the stimulated point; however, in the immediate vicinity (0.0-0.1 mm) of the stimulating electrodes, the post-synaptic response is strongly negative. A pair of stimuli has to be separated by at least 10 s to guarantee complete recovery of excitability of the post-synaptic response. The recovery curve for this response shows a refractory period of some 5 ms, a peak of excitability at an interval of about 20 ms, and then a sharp trough of relative inexcitability at about 200 ms. The post-synaptic response is considerably reduced in magnitude and duration by the addition of AP-5 to the perfusion fluid; the remaining post-synaptic response is completely abolished by kynurenic acid. The addition of bicuculline methiodide in concentrations of at least 1 x 10(-6) M increases both the magnitude and duration of the second, positive phase of the response to single stimuli. This extended positive response (which may last from 500-800 ms) is abolished by perfusion with bicuculline dissolved in Ca2(+)-free Krebs' solution. For the entire duration of the extended post-synaptic positive response produced by bicuculline, the irregular discharge of single neurons can be recorded. Like the post-synaptic positive response in Krebs' solution, the much larger response produced by bicuculline shows a very localized negativity beneath the stimulating electrodes and displays an almost identical time-course for the recovery of excitability following a single stimulus. The bicuculline induced positive response is also considerably reduced by the presence of AP-5; the addition of kynurenic acid abolishes the remaining post-synaptic response completely. A post-synaptic response, similar to that produced under bicuculline, can be produced by the addition of a maximally effective dose of d-tubocurarine.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1989

Perceptual and motor factors in the imitation of simple temporal patterns.

This study investigated the relative importance of perceptual and motor factors in the imitation of simple temporal patterns. Previous research in which subjects tap out interval sequences using one finger has suggested that perceptual factors play an important role in response timing. Studies of bimanual tapping, in contrast, stress the importance of motor interactions between the two hands. In this experiment we compared the ability of subjects to tap out two-interval sequences using one finger, two fingers on one hand, and two fingers on opposite hands. The results showed almost identical performance under the three response conditions. It is suggested that the perceptual relations between intervals in a pattern were the main determinant of performance in this experiment.

Adult↗
PubMed1988

Response characteristics of neurons in chick forebrain slices.

Coronal sections were taken from the forebrains of domestic chicks, aged 1-20 days, and maintained in vitro. Extracellular recordings of neural activity were made from the intermediate part of the medial hyperstriatum ventrale (IMHV). Spontaneous activity was rarely recorded, but neuronal responses could be evoked by stimulation of various sites. Each recording point was surrounded by an arc of sites which, when stimulated, typically elicited a short-latency field potential. These 'local responses' could be recorded in slices from chicks of any age. Stimulation of more distant sites failed to evoke field potentials from the IMHV. Instead, trains of large, unit action potentials appeared on an undisturbed baseline. Such 'unit' responses could only be evoked by stimuli delivered at specific frequencies. They required facilitation, were of variable latency, and often finally decayed. The number of sites capable of evoking a 'unit' response from the IMHV fell dramatically in slices taken from chicks older than 4 days.

Aging↗