Two experiments were conducted to investigate the effects of training on a region of the chick brain known to be critically involved in imprinting, the intermediate and medial extent of the hyperstriatum ventrale (IMHV). In the first experiment, three groups of chicks were used: (i) dark-reared (n = 9), (ii) trained for 20 min (n = 17), and (iii) trained for 140 min (n = 7). Chicks were trained by exposing them when they were approximately 21 hr old to a flashing red light. Chicks were killed when they were approximately 30 hr old and blocks of tissue were removed from the right and left IMHV. Stereological techniques were used to measure from electron micrographs the numerical density of dendritic spine and shaft synapses and the length of the postsynaptic density of these synaptic junctions. There was a significant effect of training only in the left IMHV and on only one measure, the overall mean length of the postsynaptic density of spine synapses, SPL. This measure was significantly greater by 17.2% in chicks trained for 140 min than in dark-reared controls. There was no significant effect of training for 20 min. In the second experiment one group of chicks (n = 15) was exposed to a rotating red box for a total of 3 hr. Another group of chicks was dark-reared (n = 15). The chicks were killed when they were approximately 46 hr old. Samples from the hyperstriatum accessorium and IMHV of the right and left sides were analyzed. Training was associated with a significant change, an increase, only of SPL in the left IMHV.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical Education 2010: 44: 1069–1076 Objectives  In 2006, the United Kingdom Clinical Aptitude Test (UKCAT) was introduced as a new medical school admissions tool. The aim of this cohort study was to determine whether the UKCAT has made any improvements to the way medical students are selected. Methods  Regression analysis was performed in order to study the ability of previous school type and gender to predict UKCAT, personal statement or interview scores in two cohorts of accepted students. The ability of admissions scores and demographic data to predict performance on knowledge and skills examinations was also studied. Results  Previous school type was not a significant predictor of either interview or UKCAT scores amongst students who had been accepted onto the programme (n = 307). However, it was a significant predictor of personal statement score, with students from independent and grammar schools performing better than students from state‐maintained schools. Previous school type, personal statements and interviews were not significant predictors of knowledge examination performance. UKCAT scores were significant predictors of knowledge examination performance for all but one examination administered in the first 2 years of medical school. Admissions data explained very little about performance on skills (objective structured clinical examinations [OSCEs]) assessments. Conclusions  The use of personal statements as a basis for selection results in a bias towards students from independent and grammar schools. However, no evidence was found to suggest that students accepted from these schools perform any better than students from maintained schools on Year 1 and 2 medical school examinations. Previous school type did not predict interview or UKCAT scores of accepted students. UKCAT scores are predictive of Year 1 and 2 examination performance at this medical school, whereas interview scores are not. The results of this study challenge claims made by other authors that aptitude tests do not have a place in medical school selection in the UK.

The responses to single electrical stimuli have been recorded from neurons in the brains of domestic chicks, by using an in vitro preparation consisting of a coronal slice taken from the forebrain. All slices were cut so that they contained the intermediate part of the medial hyperstriatum ventrale (IMHV). When such a slice is bathed in standard Krebs’ solution there is no evidence that the excitation produced by a single stimulus can be transmitted more than 1 mm either towards or away from the IMHV. The addition of bicuculline methiodide (more than 3 x 10 -6 M) to Krebs’ solution allows the excitation produced by a single stimulus to spread in all directions throughout the dorsal half of a coronal slice. At points remote (more than 1.5 mm) from the stimulated point, the magnitude of the spreading wave of excitation bears an all-or-nothing relation to the strength of stimulus used to excite it. This wave of excitation spreads from the excited point in all directions without attenuation at 0.9 + 0.017 (s. d.) m s -1 and consists of a prolonged burst of activity of the invaded neurons. The properties of coronal slices described above are also true of brain slices cut in a parasagittal plane. The spreading response to a single stimulus given in the presence of bicuculline, can be reduced in magnitude by the addition of AP-5 but it still spreads throughout the dorsal part of the slice at the same velocity. The response can be eliminated by the addition of kynurenic acid. The addition of curare to the bathing medium produces similar responses that spread in a similar fashion to those seen under bicuculline. These results suggest that the dorsal part of the forebrain of the domestic chick (in fact, the part derived from the embryological alar plate) contains a network of reciprocally connected local circuits. Transmission throughout the network is normally prevented by active inhibition.

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In developing Wistar albino rats, ventral horn muscle afferent boutons are lost following corticospinal innervation. Motor cortex lesions rescue a proportion of these boutons and perturb activity dependent expression of cJun and parvalbumin (PV) in the spinal cord. Therefore, we tested whether activity-dependent competition between corticospinal and proprioreceptive afferents determines the balance of these inputs to motor output pathways by delivering the inhibitory GABA agonist muscimol unilaterally to the forelimb motor cortex using slow release polymer implants from postnatal day 7 (P7) coincident with corticospinal synaptogenesis. Controls received saline. Inhibition of immature cortical neurons by muscimol was confirmed with separate in vitro electrophysiological recordings. After P28, spinal cord sections were immunostained for PV, cJun and muscle afferents transganglionically labelled with cholera toxin-B (CTB). Unilateral inhibition reduced contralaterally the number of PV positive spinal cord neurons and muscle afferent boutons in the dorsolateral ventral horn, compared to controls, and significantly altered the distribution of motoneuronal cJun expression. Separately, descending tracts were retrogradely traced with CTB from the cervical hemicord contralateral to implants. Forelimb sensorimotor cortex sections were immunostained for either CTB or PV. In muscimol treated animals, significantly fewer neurons expressed PV in the inhibited hemicortex, but as many CTB labelled corticospinal neurons were present as in controls, along with an equally large corticospinal projection from contralateral to the implant, significantly greater than in controls. Unexpectedly, unilateral inhibition of the motor cortical input did not lead to an expanded muscle afferent input. Instead, this was reduced coincident with development of a bilateral corticospinal innervation.