The visual hyperstriatal region in the chick: potentials evoked by electrical stimuli

Training chicks on a passive avoidance task modulates glutamate-stimulated inositol phosphate accumulation

The effects of glutamate, N-methyl-D-aspartate (NMDA), (+)-5-methyl-10,11-dihydro-5H-dibenzo-(a,d)-cyclo-hepten 5,10-imine maleate (MK801), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and quisqualate on the accumulation of inositol phosphates (IP) from the breakdown of phosphoinositides in vitro have been studied in tissue prisms derived from a region of the chick forebrain, the intermediate medial hyperstriatum ventrale (IMHV). In prisms from the left IMHV, glutamate stimulated IP accumulation by 10-20%, AMPA by 55% and quisqualate by 650%. These effects were more marked in the right IMHV, where AMPA stimulated IP accumulation by 157% and quisqualate by 920%. MK801 and NMDA had no significant effect on IP accumulation in either hemisphere. The left IMHV is known to be the site of a biochemical cascade resulting in synaptic remodelling following training day-old chicks on a one-trial passive avoidance task. The effect of such training was to reduce glutamate-stimulated accumulation of IP by 27% (P < 0.05) in prisms taken 30 min after training. There was no effect on prisms taken at 5 or 180 min after training, and no effect at any time in the right IMHV. MK801, injected intraperitoneally before training at a concentration known to produce amnesia for the passive avoidance task, abolished the training-induced decrease without itself affecting IP accumulation. Taken in conjunction with pharmacological and autoradiographic evidence, these results indicate that memory formation for the passive avoidance task involves the activation of NMDA receptor channels, but not quisqualate or AMPA receptors, in the left IMHV of the chick 30 min after training.

Projections of the dorsolateral anterior complex and adjacent thalamic nuclei upon the visual Wulst in the pigeon

The distinctive patterns of thalamic input to the rostral (R), intermediate (I) and caudal (C) divisions of the pigeon Wulst were determined using the retrograde multiple label technique following concomitant injections of various fluorescent tracers into different Wulst loci. The results showed topographical projections from components of the visual thalamic n. dorsolateralis anterior complex. Major ipsilateral and contralateral projections upon the R and I Wulst stem from the pars lateralis ventralis and dorsalis nuclei, respectively. The nuclei pars lateralis rostralis, pars magnocellularis and n. suprarotundus provide weak bilateral projections to all of the Wulst divisions sampled. Lastly, bilateral connections from the n. superficialis parvocellularis upon I and C, and from n. dorsolateralis posterior upon the posterior C Wulst were also demonstrated. Based upon their patterns of terminal distribution upon the Wulst, some of these thalamic nuclei are compared to specific components of the mammalian geniculate and extrageniculate visual systems.

Different rates of functional development in the two visual systems of the chicken revealed by [14C]2-deoxyglucose

Age-dependent changes in neuronal metabolic activity in the visual systems of the male chicken were assessed using [14C]2-deoxyglucose (2-DG) autoradiography. Groups of 3 and 4 chicks aged either 2 or 23 days posthatching were injected with 2 DG and exposed for 30 min to a variety of visual stimuli in either the monocular or binocular condition. Control birds had both eyes occluded. All groups were subjected to the same auditory background. In the 2-day-old chicks high levels of metabolic activity occurred in the rotundal-ectostriatal system in a manner consistent with eye use and known neuro-anatomical connections, but very low levels of activity occurred in the thalamo-hyperstriatal visual system. In the 23-day-old chicks eye use resulted in high levels of metabolic activity in both visual systems. The distribution of higher activity within the rostral regions of the anterior hyperstriatum at this age was consistent with eye use and the known distribution of ipsilateral and contralateral projections to the region. Different rates of functional development in the hyperstriatal and ectostriatal systems may reflect a requirement for different visual information processing in young versus older chickens. This study indicates that the ectostriatal system subserves the majority of early visual behavior. Age-dependent changes in the regional arrangement of activity in the Field L auditory region were also noted.

Social stress increases [14C]2-deoxyglucose incorporation in three rostral forebrain areas of the young chick

The 2-deoxyglucose method and EEG-recordings were used to compare forebrain activities between socially reared chicks, one remaining in the group the other being separated with preserved visual and auditory contact. During 30% of the test period, separated chicks produced distress calls and showed a typical EEG arousal pattern. The 9 Hz band of the EEG spectrum and the duration of distress calling were found to be significantly different from grouped chicks. Increased 2-deoxyglucose incorporation were found in 3 rostral forebrain areas of separated chicks, namely the hyperstriatum accessorium/hyperstriatum dorsale, the lateral neostriatum/hyperstriatum ventrale and the medial neostriatum/hyperstriatum ventrale. These same areas were previously reported to increase metabolic activity in imprinted Guinea fowl chicks, when they heared the imprinting stimulus during the 2-deoxyglucose experiment. It is argued that high metabolic activity in these areas reflects arousal and attention to relevant auditory or visual stimuli.