Michael Gabriel

• Ph.D.
• Professor Emeritus at University of Illinois Urbana-Champaign

It is well known that neurons of the medial geniculate (MG) nucleus of the thalamus send axonal projections to the amygdala. It has been proposed that these projections supply information that supports amygdalar associative processes underlying acquisition of acoustically cued conditioning and learning. Here we demonstrate the reverse direction of...

This study addressed the neural mediation of discriminative avoidance learning, wherein rabbits step in a wheel apparatus in response to an acoustic conditional stimulus, the CS+, to avoid a foot shock, and they learn to ignore a different stimulus, the CS-, not followed by foot shock. Previously, muscimol-induced inactivation of the amygdala in th...

Cingulothalamic neurons develop topographic patterns of cue-elicited neuronal activity during discrimination learning. These patterns are context-related and are degraded by hippocampal lesions, suggesting that hippocampal modulation of cingulothalamic activity results in the expression of the patterns, which could promote the retrieval of context-...

Neuronal activity of the auditory thalamus, amygdala, cingulate cortex, and substantia nigra was recorded during the administration of a behavioral test for latent inhibition (LI) or the retardation of behavioral conditioning because of preexposure of the conditional stimulus (CS). Following CS preexposure, both the preexposed CS and a control CS p...

Multiple-unit neuronal activity was recorded from three “nonspecific” polysensory regions of the cerebral cortex of rabbit during a test for stimulus generalization of an avoidance CR. Behavioral and cortical data obtained during the acquisition of the CR were reported in a previous paper. These data showed acquisition and maintenance of cortical m...

Two groups were formed from a large sample of rabbits used as subjects in ongoing studies of the neural correlates of discriminative avoidance conditioning and reversal. The members of one group (N = 9) received conditioning to criterion, whereas members of the second group (N = 9) received conditioning to criterion followed by three sessions of ov...

Independent groups of albino rabbits were trained to an avoidance criterion using a 1000 cps pure tone CS. Independent subgroups were extinguished with tones of 1000, 2000, or 4000 cps either. 5, 12, 24, or 48 h after training. Resistance to extinction for 1000 cps was least after a. 5 h intersession delay (ISD) and greatest after 24 h ISD did not...

Neuronal activity of the anterior cingulate (AC) region of the rabbit cerebral cortex was recorded during differential conditioning and reversal of a behavioral avoidance response. Discriminative neuronal activity, in the form of a greater neuronal response to CS+ relative to CS—, occurred in the intermediate and final sessions of original conditio...

The performance of conditioned responses (CRs) is diminished when trained subjects are tested in a novel context. This study tested the hypothesis that the flow of contextual information along the disynaptic "ESA" (entorhinal cortex-ventral subiculum-nucleus accumbens) pathway is responsible for context-related modulation of CRs. Rabbits received e...

Arrowsmith is a unique computer-assisted strategy designed to assist investigators in detecting biologically-relevant connections between two disparate sets of articles in Medline. This paper describes how an inter-institutional consortium of neuroscientists used the UIC Arrowsmith web interface http://arrowsmith.psych.uic.edu in their daily work a...

This study addressed the amygdala's role in avoidance conditioning in rabbits (Oryctolagus cuniculus). Intra-amygdalar muscimol infusion before 60 or 120 conditioning trials blocked training-induced neuronal activity (TIA) in the medial geniculate (MG) nucleus. One hundred twenty trials with muscimol blocked TIA permanently, during conditioning wit...

Images, 2D or 3D, are usually perceived or analyzed in their respective number of dimensions either in the spatial domain or frequency domain. 3D images such as volumetric data sets are important in many scientific and biomedical fields. To extend a 2D image compression coder to 3D, special care is often required. We are proposing a progressive los...

Theta rhythmicity of field potentials recorded in the posterior cingulate cortex is thought to have a septo-hippocampal origin, principally because phase reversal of this theta occurs in the dorsal hippocampus, but not in the posterior cingulate cortex. In the current study, theta activity of cue-elicited field potentials and multiple unit activity...

A brain anatomical image sequence obtained through histology posed a new challenge to medical image registration. Aligning hundreds to thousands of image slices using a pairwise registration technique may cause error propagation or introduce random error. Information across multiple adjacent image slices must be considered for the alignment. We dev...

Optimization is a key component of image registration. Due to the non-convexity and high computation cost of the objective function, a common tactic is to set an initial guess and then use multi-resolution or local optimization methods to find a local optimum of the objective function. For almost all local optimization methods, the initial location...

3D neuro-anatomical images and other volumetric data sets are important in many scientific and biomedical fields. To achieve a high compression rate, near-lossless or lossless compression algorithm is applied which uses a Hilbert traversal to produce a data stream from the original image. An extremely fast linear DPCM is used. The linear DPCM takes...

Daily injections of cocaine administered to pregnant rabbits (Oryctolagus cuniculus) throughout gestation were associated with neural and behavioral changes during development and in adulthood, including altered neuron structure and function in areas receiving dopaminergic projections and retarded Pavlovian eyeblink conditioning with low-salient co...

This paper considers issues arising from presentations by Barry Everitt and Gorica Petrovich concerning amygdalar involvement in appetitive conditioning. Studies reported by these researchers are beginning to unravel the distribution of associative functions among amygdalar nuclei and their efferent targets. The main issue addressed here concerns h...

A substantial literature implicates the anterior and mediodorsal (limbic) thalamic nuclei and the reciprocally interconnected areas of cingulate cortex in learning, memory, and attentional processes. Previous studies have shown that limbic thalamic lesions severely impair discriminative avoidance learning and that they block development of training...

The volumetric data set is important in many scientific and biomedical fields. Since such sets may be extremely large, a compression method is critical to store and transmit them. To achieve a high compression rate, most of the existing volume compression methods are lossy, which is usually unacceptable in biomedical applications. We developed a ne...

In this paper, we present a neuro-medical imaging system called the Brain Slicer, which allows neuroscientists to construct a three-dimensional digital brain atlas from an array of high-resolution parallel section images and obtain arbitrary oblique section images from the digital atlas. This application is based on a new data structure, the Scalab...

The amygdala is critically involved in discriminative avoidance learning. Large lesions of the amygdala block discriminative avoidance learning and abolish cingulothalamic training-induced neuronal activity. These results indicated that amygdalar processing is critical for cingulothalamic plasticity. The larger lesions did not allow differentiation...

Earlier studies of human infants and studies employing animal models had indicated that prenatal exposure to cocaine produced developmental changes in the behavior of the offspring. The present paper reports on the results obtained in a rabbit model of in utero exposure to cocaine using intravenous injections (4 mg/kg, twice daily) that mimic the p...

Neurons in particular layers of cingulate cortex and in limbic thalamic nuclei exhibit peak firing rates in response to a positive conditional stimulus (CS+) in particular stages of discriminative learning. A given area is maximally activated by the CS+ in the initial, an intermediate, or a late stage of behavioral acquisition, and activation in al...

Whereas the amygdala is generally understood to be involved in aversively motivated learning, the specific associative function of the amygdala remains controversial. This study addressed the amygdalar role in mediation of discriminative instrumental avoidance learning of rabbits. Bilateral microinjection of the GABA receptor agonist muscimol cente...

We applaud Aggleton & Brown's affirmation of limbic diencephalic-hippocampal interaction as a key memory substrate. However, we do not agree with a thesis of diencephalic-hippocampal strict dedication to episodic memory. Instead, this circuitry supports the production of context-specific patterns of activation that subserve retrieval for a bro...

Neuronal activity was recorded in the cingulate cortex and the limbic thalamus in Dutch-belted rabbits (Oryctolagus cuniculus) exposed to cocaine (8 mg/kg/day i.v.) or saline in utero during acquisition and reversal learning of a discriminative avoidance response. Anterior cingulate cortical excitatory training-induced activity (TIA) was attenuated...

Cingulate cortex and related areas of the thalamus are critically involved in the mediation of discriminative avoidance learning, wherein rabbits step in response to an acoustic conditional stimulus (CS+) to avoid foot shock and they learn to ignore a different acoustic stimulus (CS-) not followed by shock. Studies of multi-unit neuronal activity r...

Two experiments assessed the effects of 1) combined subicular complex and posterior cingulate cortical lesions on training-induced neuronal activity (TIA) in the anterior ventral (AV) and medial dorsal (MD) thalamic nuclei; 2) hippocampal (Ammon's horn and dentate gyrus) lesions on TIA in cingulate cortex and in the AV and MD thalamic nuclei. The r...

This study assessed the role of the thalamic medial geniculate (MG) nucleus in discriminative avoidance learning, wherein rabbits acquire a locomotory response to a tone [conditioned stimulus (CS)+] to avoid a foot shock, and they learn to ignore a different tone (CS-) not predictive of foot shock. Limbic (anterior and medial dorsal) thalamic, cing...

Learning to fear dangerous situations requires the participation of neurons of the amygdala. Here it is shown that amygdalar neurons are also involved in learning to avoid dangerous situations. Amygdalar lesions severely impaired the acquisition of acoustically cued, discriminative instrumental avoidance behavior of rabbits. In addition, the develo...

 Rabbits given either electrolytic lesions of the entorhinal cortex or sham-lesions were trained to prevent a foot-shock by stepping in an activity wheel after one tone, a positive conditioned stimulus (CS+), and to ignore a different tone, a negative conditioned stimulus (CS–). Neuronal activity was recorded simultaneously in the basolateral nucle...

Combined lesions of the medial dorsal and anterior thalamic nuclei severely impair the acquisition of discriminative avoidance behavior, wherein rabbits learn to prevent foot-shock by stepping after a tone conditional stimulus (CS+), and they learn to ignore a different tone (CS-) that does not signal foot-shock. Neurons in these thalamic nuclei ex...

In a previous study, lesions of the deep cerebellar nuclei blocked classical eyeblink conditioning, but did not impair discriminative avoidance learning in rabbits. Here, was also found previously, lesions of the anterior and medial dorsal thalamic nuclei severely impaired discriminative avoidance learning. However, these lesions had no impact on d...

Stimulation in the human somatosensory thalamus, posteroinferior to the human principal sensory nucleus (ventralis caudalis), has been reported to reproduce previously experienced pain associated with a strong affective dimension. In these reports, pains with a strong affective dimension were reproduced by stimulation within and posteroinferior to...

Previous research employing lesions and recording of neuronal activity has implicated cingulothalamic and hippocampal circuitry in the mediation of discriminative instrumental avoidance learning in rabbits. This study was directed at the question of whether the cingulothalamic circuitry is specialized for avoidance learning, or whether it is also i...

Neuronal discharges related to acoustic conditional stimuli and locomotive behavioral responses of 152 anterior and medial dorsal (MD) thalamic and cingulate cortical single-units sorted from multi-unit activity were recorded as rabbits performed in a discriminative avoidance task. The goals were: (1) to document the single-unit constituents of mul...

This study assessed the context specificity of learning-related neuronal activity: whether the same physical stimuli would elicit different neuronal responses depending on the learning situation. Neuronal activity was recorded simultaneously in six limbic areas as rabbits learned to approach a spout for water reinforcement after a tone (CS+) and to...

Multiunit activity of cingulate cortex and the anterior ventral (AV) thalamic nucleus was recorded as rabbits learned to avoid a shock by locomoting in response to a tone (CS+) and to ignore a nonpredictive tone (CS-). Rabbits with anterior dorsal (AD) thalamic lesions avoided shock more often than controls during the first training session and the...

Rabbits with bilateral transecting lesions of the mamillothalamic tract, control (tract-sparing and sham) lesions, or no lesions, and chronic, fixed-position anterior ventral (AV) and medial dorsal (MD) thalamic and posterodorsal subicular complex unit recording electrodes were trained to step in an activity wheel in response to a 0.5 sec tone (CS+...

This study was designed to determine whether axons of cholinergic dorsal tegmental neurons terminate on cells in the anterior thalamus in rabbits as in other species, and to localize projecting tegmental cells for future studies of their contributions to anterior thalamic learning-relevant neuronal activity. The distribution of retrogradely labeled...

discriminative training procedures bring about the acquisition of discriminative brain activity, i.e., different patterns of neuronal activity in response to the differentially predictive stimuli / electrophysiological mapping can be used to identify the neurons and circuits that exhibit discrimination between these categories of stimuli / document...

Multi-unit neuronal activity was recorded in posterior cingulate cortex (area 29) and the anterior ventral (AV) thalamic nucleus during discriminative instrumental avoidance learning wherein a response (stepping in an activity wheel) to a 0.5-s tone (CS+) prevented a foot-shock 5 s after CS+ onset. Presentations of a different tone (CS-) on 50% of...

This project is part of an ongoing experimental analysis of the neural mediation of learning and memory. The overall objective is to document the learning-relevant dynamic physiological changes in brain circuit activities that mediate discriminative avoidance learning in rabbits. Electrophysiological multichannel recording of neuronal activity duri...

This study is part of an ongoing project concerned with the analysis of the neural substrates of discriminative avoidance learning in rabbits. Multi-unit activity was recorded in 5 anterior and lateral thalamic nuclei and in 4 layers of 2 posterior cingulate cortical areas (29c/d and 29b) during learning. The rabbits learned to step in response to...

Cerebellar interpositus nucleus lesions were given to 14 rabbits trained in two behavioral paradigms; discriminative avoidance conditioning of locomotor behavior and classical nictitating membrane conditioning. Bilateral lesions that prevented acquisition of the classically conditioned response on both the left and right side failed to affect the a...

Training-induced neuronal activity develops in the mammalian limbic system during discriminative avoidance conditioning. This study explores behaviorally relevant changes in muscarinic ACh receptor binding in 52 rabbits that were trained to one of five stages of conditioned response acquisition. Sixteen naive and 10 animals yoked to criterion perfo...

Basolateral (BL) amygdaloid multi-unit activity was recorded as male albino rabbits learned to avoid a foot-shock unconditioned stimulus (US) by stepping in an activity wheel to an acoustic (pure tone) warning stimulus (CS+). A second tone (CS-) of different auditory frequency than the CS+ was presented in an irregular order on half of the conditio...

This study extends an ongoing analysis of the neural mediation of discriminative avoidance learning in rabbits. Electrolytic lesions encompassing anterior and posterior cingulate cortex (area 24 and 29) or ibotenic acid lesions in area 24 only were made prior to avoidance conditioning wherein rabbits learned to step in response to a tone conditiona...

Neuronal activity in cingulate cortex was recorded during discriminative active avoidance conditioning of rabbits. In one subpopulation of neurons, brief (200 and 500 ms) conditional stimuli (CSs) elicited greater average cingulate cortical training-induced neuronal discharges during conditioned response acquisition than did a long (5,000 ms) CS, a...

Rabbits previously trained to asymptotic performance of discriminative active avoidance behavior (n = 8) received systemic injections of scopolamine hydrobromide (SH: 1.0, 2.0, or 4.0 mg/kg) and scopolamine methylbromide (SM: 4.0 mg/kg). Each rabbit received all of the doses in a counterbalanced order. Single injections were administered 30 min bef...

This chapter focuses on the functions of anterior and posterior cingulate cortex during avoidance learning in rabbits. The task is administered as rabbits occupy a running wheel, a replica of an apparatus. To study the neuronal events that support this learning, multi-unit and single-unit activity is recorded simultaneously in several brain areas d...

Multi-unit and field potential responses in the anterior (AC) and posterior cingulate cortices (PC), dentate gyrus (DG), and anterior ventral (AV) and medial dorsal (MD) thalamic nuclei of rabbits were recorded during acquisition and performance of a locomotor conditioned response (CR). The CR, stepping in an activity wheel in response to a tone (c...

Four groups of male albino rabbits were trained to perform a conditioned response (CR, stepping in an activity wheel) to an acoustic (pure tone) conditional stimulus (CS+). A 1.5-2.0 mA shock unconditional stimulus (US) delivered through the grid floor of the wheel was administered 5 s after CS+ onset, but stepping during the CS-US interval prevent...

The frequency of multi-unit neuronal firing in response to tonal conditional stimuli increases, and the neuronal responses become discriminative in character, in the anterior and posterior subfields of the cingulate cortex (Brodmann's Area 24 and 29, respectively) during the course of discriminative avoidance conditioning in rabbits. Bilateral elec...

Past studies of the neural determinants of discriminative avoidance conditioning in rabbits have fostered a theoretical model that describes the interactive functioning of the cingulate cortex (Brodmann's Areas 24 and 29), the anterior ventral and medial dorsal thalamic nuclei (AVN and MDN) and the hippocampus. Here we test hypotheses of the model...

The neuronal discharge that develops in the anterior ventral thalamic nucleus (AVN) in response to a task-relevant stimulus during learning is enhanced in rabbits with damage in the cingulate and subicular (hippocampal) cortical areas that project to this nucleus. These results indicate that the corticothalamic projections limit the anterior thalam...

Multiple-unit activity in the reticular formation of the midbrain and pons was recorded in rabbits during discriminative conditioning of locomotor (wheel-running) avoidance behavior. The conditional stimuli (CS+ and CS-) were pure tones of different auditory frequency, and the unconditional stimulus (US) was a constant-current footshock (1.5-2.5 mA...

The information in this chapter is based on studies of the neural correlates of conditioned avoidance behavior in rabbits. The results have fostered a conceptualization of the functional relevance of the hippocampus to avoidance behavior, and to learning and memory processes considered more generally.

Bilateral electrolytic lesions of the anteroventral (AV) nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had developed in the cingulate a...

Multiple-unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) thalamic nucleus was recorded during reversal training following differential conditioning of a locomotory (wheel rotation) avoidance response in rabbits. The positive and negative conditional stimuli (CS+ and CS-) were pure tones and the unconditional stimulus (UCS) was...

Multiple-unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) thalamic nucleus was recorded during discriminative conditioning of a locomotory avoidance response in rabbits. A major objective was to compare the results with those previously obtained from the posterior limbic (cingulate) cortex, and the anteroventral (AV) thalamic n...

Bilateral electrolytic lesions of the anteroventral nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of 12 male New Zealand White rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had develop...

Multiple unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) nucleus of the thalamus was recorded during differential conditioning of a locomotory (wheel-rotation) avoidance response. The positive and negative conditional stimuli (CS+ and CS-) were pure tones (l kHz and 8 kHz), and the unconditional stimulus was a footshock (1.5-2...

Multiple-unit activity of the cingulate cortex and the anteroventral (AV) nucleus of the thalamus in rabbits was recorded during reversal training, following differential conditioning of a locomotory (wheel rotation) avoidance response. The CS+ and CS- were pure tones (1 or 8 kHz) and the UCS was a footshock delivered through the grid floor of the...

Electrolytic lesions of the anteroventral (AV) nucleus of the thalamus impaired significantly retention performance of rabbits in a discriminative avoidance task. In addition the lesions abolished the excitatory, discriminative neuronal discharges which had developed in the cingulate cortex during the course of behavioral acquisition, prior to the...

Multiple-unit activity of the cingulate cortex and the anteroventral (AV) nucleus of the thalamus was recorded during discriminative conditioning of an avoidance response (locomotion) in rabbits. The results indicated a greater unit response in cingulate cortex to the positive conditional stimulus (CS+; a tone paired with a footshock unconditional...