Altered activity in the hippocampus is more detrimental to classical conditioning than removing the structure.

Hippocampal ablation has no effect on the acquisition of the rabbit's classically conditioned nictitating membrane response. Systemic administration of scopolamine, which alters hippocampal neuronal activity, severely retards acquisition of the conditioned response in normal animals and those with cortical ablations. In animals with hippocampal ablations, however, scopolamine has no effect on conditioning. These findings suggest that altered neuronal activity in the hippocampus is more detrimental to conditioning than removing the structure.

Polymorphism in ADH and MTHFR genes in oral squamous cell carcinoma of Indians.

OBJECTIVES: Alcohol consumption is known to increase the risk for several cellular disorders like oral cancer. The risk may be reinforced by polymorphism in genes like alcohol dehydrogenase. Therefore, this study is designed to asses the polymorphic status in ADH1B (formerly ADH2), ADH1C (formerly ADH3) and MTHFR genes in order to correlate the susceptibility to oral squamous cell carcinoma (OSCC). SUBJECTS AND METHODS: DNA from 126 OSCC samples were amplified using primers for ADH1B, ADH1C and MTHFR genes. The amplicons were analyzed for ADH1B*1, ADH1C*2 and MTHFR C677T allelic polymorphism by restriction digestion using appropriate enzymes. RESULTS: ADH1B*1/*1 genotype in cancer patients who were heavy drinkers showed a negligible risk association with an odds ratio of 1.62; 95% CI = 1.08-2.14. In OSCC patients, ADH1C*2/*2 genotypes showed a relatively higher risk (odds ratio 2.65; 95% CI = 1.78-3.53) in heavy drinkers and a less significant risk (1.6; 95% CI = 1.15-2.03) in moderate drinkers and negligible risk in light drinkers (1.23; 95% CI = 0.77-1.63). In contrast, MTHFR 677TT genotype showed a high risk association for OSCC in heavy drinkers (odds ratio 3.0; 95% CI = 2.02-4.0). Interestingly, the combination of ADH1B*1/*1/ MTHFR 677TT genotypes in alcoholic cancer patients showed a high risk (odds ratio 4.16; 95% CI = 2.78-5.53). A similar risk (odds ratio 4.16; 95% CI = 1.18-5.53) was shown by ADH1B*1/*2/*2/*2MTHFR 677TT genotype combination. The ADH1C*2/*2 /MTHFR 677TT genotype combination showed the maximum risk (odds ratio 20; 95% CI = 13.45-26.64) in the heavy drinker group. This combination showed a high risk in moderate drinkers (odds ratio 5.88; 95% CI = 4.24-7.50) and relatively lower risk in light drinkers (odds ratio 2.77; 95% CI = 1.74-3.68). CONCLUSIONS: The ADH1C*2/*2/MTHFR 677TT genotype combination appears to be more susceptible for OSCC, since it showed a 20-fold increase in risk in heavy drinkers and a 5.9- and 2.8-fold increase in risk respectively in moderate drinkers and light drinkers. This study suggests the association of ADH1C*2/*2/MTHFR 677TT genotype combination as a risk factor for OSCC in alcoholics.

Promoter hypermethylation analysis in myelodysplastic syndromes: diagnostic & prognostic implication.

BACKGROUND & OBJECTIVE: Myelodysplastic syndromes (MDS) are a heterogenous group of haematopoietic stem cell disorders that are multifactorial in their aetiology. Unique genetic alterations in combinations or in isolation account for a small fraction of MDS suggesting the epigenetic hypermethylation as a possible leading cause for MDS and its transformation to acute myelocytic leukaemia (AML). Therefore, in this study, promoter hypermethylation status of key cell cycle regulators was assessed as markers in MDS patients and association of hypermethylation with clinical progression of disease was also studied. METHODS: Promoter hypermethylation analysis of five tumour associated genes namely p16, p15, MGMT, hMLH1 and E-cadherin were done for 41 MDS patient samples with its various subtype. The hypermethylation analysis was done by using semi-nested multiplex PCR. RESULTS: Eighty per cent of (33/41) of the MDS samples were found to be methylated in any one of the four genes (p16, p15, MGMT and E-cadherin). The p15 methylation was found to be the most frequent 61 per cent (25/41), E-cadherin was methylated in 39 per cent (16/41) and p16 in 37 per cent (15/41) of the cases. MGMT gene showed a low 5 per cent (2/41) methylation whereas hMLH1 gene was not methylated in any one of the samples analysed. INTERPRETATION & CONCLUSION: Differential rate of methylation of the four genes (p16, p15, MGMT and E-cadherin) was observed in MDS samples. All the samples analysed showed the absence of a methylator phenotype in MDS. The methylation frequency of all these genes increased with the clinical severity of the MDS subtypes. Therefore, hypermethylation may be used as a diagnostic and prognostic tool in ascertaining the clinical severity of MDS.

Differential effects of microinjections of d-amphetamine into the nucleus accumbens or the caudate putamen on the rat's ability to ignore an irrelevant stimulus.

Latent inhibition is an attentional process by which animals learn to ignore an irrelevant stimulus. Rats received either 0 or 30 preexposures to a tone which was later used as a conditioned stimulus (CS) in a two-way avoidance task. Tone preexposure resulted in retarded conditioning (i.e., latent inhibition) in animals which received microinjections of saline or amphetamine in the caudate-putamen and for those which received microinjections of saline in the nucleus accumbens. This latent inhibition effect, however, was not present in animals which received d-amphetamine microinjections in the nucleus accumbens. The failure of CS preexposure to retard conditioning in these animals was not due to drug-induced changes in either tone or shock sensitivity. The results are discussed in terms of the role of the mesolimbic dopamine system in learning to ignore an irrelevant stimulus and the use of LI as a possible animal model of the attentional deficit that seems to characterize some subpopulations of schizophrenic humans.

Disruption of selective attention in the rat following chronic d-amphetamine administration: relationship to schizophrenic attention disorder.

In the blocking paradigm, prior training to one conditioned stimulus (CSA) blocks the ability to attend to a second conditioned stimulus (CSB) when the two form a compound (CSAB) in subsequent training. Blocking is an associative process by which animals learn to ignore CSB because it contains no new information regarding the reinforcing event. Experiment 1 showed that d-amphetamine disrupted rats' ability to ignore the irrelevant CSB: The animals responded equally to both elements of the CSAB compound following five dialy administrations of 4 mg/kg d-amphetamine. In Experiment 2 the disruption of blocking by d-amphetamine was eliminated by concomitant administration of 0.02 mg/kg haloperidol. These results are consistent with previous research showing that d-amphetamine disrupts rats' ability to ignore repeated presentations of a single nonreinforced stimulus in the latent inhibition paradigm. The inability of amphetamine-treated animals to ignore one element of a dual-element compound bears some resemblance to selective attention deficits seen among schizophrenic patients.

Disrupted latent inhibition in the rat with chronic amphetamine or haloperidol-induced supersensitivity: relationship to schizophrenic attention disorder.

Latent inhibition (LI) is an attentional process by which animals learn to ignore a stimulus that is repeatedly presented without reinforcement. This ability to tune out a motivationally irrelevant stimulus is disrupted by pharmacological manipulations producing hyperdopaminergic states. In Experiment I, LI was disrupted following five daily administrations of 4 mg/kg d-amphetamine. In Experiment II the disruptive effects of d-amphetamine were eliminated by concomitant administration of chlorpromazine. Experiment III showed that LI could also be disrupted with 1 mg/kg d-amphetamine coupled with dopamine receptor supersensitivity produced by prolonged pretreatment with haloperidol. These data suggest that pharmacological disruption of LI may provide an animal analogue of the defective stimulus filtering thought to characterize at least some forms of schizophrenia.

Disrupted retention of the classically conditioned nictitating membrane response in the aluminum-intoxicated rabbit using electrical stimulation of the brain as a conditioned stimulus.

Rabbits were classically conditioned to emit an eyeblink conditioned response (CR) to electrical stimulation (ESB) of the medial geniculate nucleus (MGN) paired with a corneal air puff until they attained a criterion of two consecutive days of greater than 90% CRs. They then received intraventricular injections of 1% AlCl3, HCL, or normal saline. Ten days postinjection, each animal underwent a retention test consisting of 50 ESB alone presentations. Whereas all saline and HCL animals gave at least 90% CRs during retention, no aluminum rabbit emitted more than 30% CRs. Considered with the results of previous work, these data suggest that aluminum-induced neurofibrillary degeneration disrupts retention of the CR by affecting central associative processes.

Disruption of classical conditioning in patients with Alzheimer's disease.

One of the primary features of Alzheimer's disease (AD) is a disorder of memory. Although considerable effort has been devoted to characterizing this memory disorder, simple forms of memory such as classical (Pavlovian) conditioning have not been studied. The prevailing view has been that these simple forms of memory are not affected in AD. These forms of memory, however, may be of particular interest because they are beginning to be well understood at the neurobiological level. Because of this, when memory disorders are detected, it may be possible to specify their neurobiological substrate. We now report that classical conditioning of the eyeblink response is disrupted in AD patients compared to age-matched controls. This deficit in conditioning is not due to nonassociative factors such as changes in sensitivity to stimuli or disruption of the motor response. The results are considered in terms of using simple forms of memory to help generate hypotheses regarding the neurobiology of age-related memory disorders.

Age-related disruption of classical conditioning: a model systems approach to memory disorders.

The model systems approach to the neurobiology of memory involves studying a well characterized learned response in a relatively simple and well controlled preparation. The best characterized mammalian model system is classical conditioning of the rabbit's eyeblink response. Using this preparation, significant progress has been made toward understanding the neurobiological systems and mechanisms involved in elaboration of the conditioned response. Using a well characterized model system such as classical eyeblink conditioning, it should be possible to both characterize the changes in learning and memory that accompany aging and to investigate their neural substrates. Our strategy for using the conditioned eyeblink preparation for studying age-related memory deficits is four-fold and includes investigating conditioning deficits in: (1) humans across the life span, (2) rabbits across the life span, (3) Alzheimer's disease patients, and (4) rabbits with aluminum-induced neurofibrillary degeneration. In this paper, we present exemplary data from each of these lines of research. If similar deficits occur in each of these groups, it may be possible to begin to form hypotheses about the neurobiology of age-related memory disorders.

Nimodipine facilitates retention of the classically conditioned nictitating membrane response in aged rabbits over long retention intervals.

Aged rabbits initially underwent 18 days of acquisition of the classically conditioned nictitating membrane response (NMR) using a tone conditioned stimulus (CS) and an air puff unconditioned stimulus (UCS). They were then treated with a low or high dose of nimodipine or a vehicle for 90 days. During this time no further CS-UCS pairings were presented. They underwent testing for retention of the conditioned response (CR) at 30 and 90 days. Retention testing consisted of 20 presentations of the CS alone. Rabbits in the control condition retained 46.4% of their predrug levels of conditioned responding and rabbits receiving the low dose of nimodipine retained 37.3% of their predrug levels after 30 days. After 90 days, retention in these animals declined to 8.1% and 14.1%, respectively. In contrast, rabbits receiving the high dose of nimodipine retained 85% of their predrug learning at 30 days with little decline at 90 days (77.1%). Nonassociative factors such as sensitivity to the CS or UCS could not explain these effects.

A 7 minute neurocognitive screening battery highly sensitive to Alzheimer's disease.

OBJECTIVE: To determine the validity and reliability of a rapidly administered neurocognitive screening battery consisting of 4 brief tests (Enhanced Cued Recall, Temporal Orientation, Verbal Fluency, and Clock Drawing) to distinguish between patients with probable Alzheimer's disease (AD) and healthy control subjects. SUBJECTS: Sixty successive referrals to the Memory Disorders Clinic at Southwestern Vermont Medical Center, Bennington, who were diagnosed as having probable AD and 60 community-dwelling volunteers of comparable age, sex distribution, and education. DESIGN: Interrater and test-retest reliability, intergroup comparisons between patients with AD and control subjects on the 4 individual tests, and determination of probability of dementia for patients with AD and control subjects using the entire battery of tests. SETTING: Outpatient care. MAIN OUTCOME MEASURE: Comparison of the probability of dementia on the 7 Minute Screen with the criterion standard of clinical diagnosis established by examination and laboratory studies. SECONDARY OUTCOME MEASURES: Test-retest and interrater reliability (correlation coefficients), time for administration. RESULTS: Mean time of administration was 7 minutes 42 seconds. Mean scores for patients with AD and control subjects on all 4 individual tests were significantly different (for each, P<.001). When the 4 tests were combined in a logistic regression, the battery had a sensitivity of 100% and a specificity of 100%. A series of 1000 repeated random samples of 30 patients with AD and 30 control subjects taken from the overall sample of 60 patients with AD and 60 control subjects had a mean sensitivity of 92% and a mean specificity of 96%. The battery was equally sensitive to patients with mild AD as demonstrated by correctly classifying all 13 patients with AD using Mini-Mental State Examination scores of 24 or higher. Neither age nor education was a statistically significant factor when added as a covariate. Test-retest reliabilities for individual tests ranged from 0.83 to 0.93. Test-retest reliability for the entire battery was 0.91. Interrater reliability for the entire battery was 0.92. CONCLUSIONS: The 7 Minute Screen appears highly sensitive to AD and may be useful in helping to make initial distinctions between patients experiencing cognitive changes related to the normal aging process and those experiencing cognitive deficits related to dementing disorders such as AD. It has reasonable interrater and test-retest reliability, can be administered in a brief period, and requires no clinical judgment and minimal training.

A 5-month, randomized, placebo-controlled trial of galantamine in AD. The Galantamine USA-10 Study Group.

OBJECTIVE: To investigate the efficacy and tolerability of galantamine, using a slow dose escalation schedule of up to 8 weeks, in 978 patients with mild to moderate AD. METHODS: A 5-month multicenter, placebo-controlled, double-blind trial. Following a 4-week placebo run-in, patients were randomized to one of four treatment arms: placebo or galantamine escalated to final maintenance doses of 8, 16, or 24 mg/day. Outcome measures included the cognitive subscale of the AD Assessment Scale (ADAS-cog), the Clinician's Interview-Based Impression of Change plus Caregiver Input (CIBIC-plus), the AD Cooperative Study Activities of Daily Living inventory, and the Neuropsychiatric Inventory. Standard safety evaluations and adverse event monitoring were carried out. RESULTS: After 5 months, the galantamine-placebo differences on ADAS-cog were 3.3 points for the 16 mg/day group and 3.6 points for the 24 mg/day group (p < 0.001 versus placebo, both doses). Compared with placebo, the galantamine 16- and 24-mg/day groups also had a significantly better outcome on CIBIC-plus, activities of daily living, and behavioral symptoms. Treatment discontinuations due to adverse events were low in all galantamine groups (6 to 10%) and comparable with the discontinuation rate in the placebo group (7%). The incidence of adverse events in the galantamine groups, notably gastrointestinal symptoms, was low and most adverse events were mild. CONCLUSIONS: Galantamine 16 and 24 mg/day significantly benefits the cognitive, functional, and behavioral symptoms of AD as compared with placebo. Slow dose escalation appears to enhance the tolerability of galantamine, minimizing the incidence and severity of adverse events.

Neurochemical characteristics of aluminum-induced neurofibrillary degeneration in rabbits.

Aluminum-induced neurofibrillary degeneration in rabbits is known to affect particular populations of neurons. The neurotransmitter alterations which accompany aluminum neurofibrillary degeneration were examined in order to assess how closely they mimic those of Alzheimer's disease. There was a significant reduction in choline acetyltransferase activity in entorhinal cortex and hippocampus as well as significant reductions in cortical concentrations of serotonin and norepinephrine in the aluminum-treated rabbits. Significant reductions in glutamate, aspartate and taurine were found in frontoparietal and posterior parietal cortex. Concentrations of GABA were unchanged in cerebral cortex. Both substance P and cholecystokinin immunoreactivity were significantly reduced in entorhinal cortex but there were no significant changes in somatostatin, neuropeptide Y and vasoactive intestinal polypeptide. The five neuropeptides were unaffected in striatum, thalamus, cerebellum and brainstem. Neurochemical changes were found in the regions with the most neurofibrillary degeneration while regions with little or no neurofibrillary degeneration were unaffected. The reductions in choline acetyltransferase activity, serotinin and noradrenaline suggest that some neuronal populations preferentially affected in Alzheimer's disease are also affected by aluminum-induced neurofibrillary degeneration; however, the cortical somatostatin deficit which is a feature of Alzheimer's disease is not replicated in the aluminum model.

Hippocampus, context, and conditioning.

Rabbits (Oryctolagus cuniculus) with lesions to either the hippocampus or overlying neocortex and unoperated controls underwent acquisition of the classically conditioned nictitating membrane response to a tone conditioned stimulus and an air puff unconditioned stimulus until they reached a criterion of 8 conditioned responses in any block of 10 trials. They were then returned to their cages. On the next day, they were either placed in the same context in which they underwent initial conditioning or switched to a new context that distinctly differed along olfactory, visual, and tactile dimensions. In relation to unswitched controls, rabbits with lesions to the neocortex and unoperated controls showed a disruption of conditioning when contexts were switched. In contrast, rabbits with lesions to the hippocampus performed at the same levels as unswitched controls. The results are discussed in terms of the possible role of hippocampus in coding context in classical conditioning.

Age-related disruption of trace but not delay classical conditioning of the rabbit's nictitating membrane response.

Young (6 months of age) and old (36-60 months) New Zealand albino rabbits underwent classical conditioning of the nictitating membrane response in either a delay conditioning (Experiment 1) or a trace conditioning (Experiment 2) paradigm. There was no difference between old and young animals in acquisition of the conditioned response in the delay paradigm, nor were there any age-related differences in generalization to the tone conditioned stimulus (CS) or in sensitivity to the tone CS or eye shock unconditioned stimulus. In the trace conditioning paradigm, however, old animals acquired the conditioned response significantly more slowly than young rabbits. Because the same stimulus parameters and the same response were used in both experiments, it is unlikely that age-related differences in trace conditioning were due to stimulus sensitivity, motivation, or fatigue. The results are discussed in terms of how brain changes that accompany aging could differentially affect these two types of classical conditioning.

A selective attention deficit in the rat following induced dopamine receptor supersensitivity.

In the blocking paradigm, prior training to one conditioned stimulus (CSA) blocks the ability to attend to a second conditioned stimulus (CSB) when the two form a compound (CSAB) in subsequent training. Blocking is an associative process by which animals learn to ignore CSB because it contains no new information regarding the reinforcing event. In Experiment 1, dopamine (DA) receptor supersensitivity was induced in rats by prolonged pretreatment with haloperidol. The animals with DA receptor supersensitivity failed to show blocking by responding equivalently to both elements of the CSAB compound. This effect was replicated in Experiment 2, which also tested for an arousal interpretation of disrupted blocking by introducing a novel stimulus following training. Supersensitive rats were no more responsive to this novel stimulus than were control animals, which supports a selective attention deficit interpretation of disrupted blocking with DA receptor supersensitivity. This attentional deficit resembles behavioral perseverations induced by DA agonists.

Classic conditioning in aged rabbits: delay, trace, and long-delay conditioning.

Young (0.5 years) and aged (2+, 3+, and 4+ years) rabbits underwent acquisition of the classically conditioned nictitating membrane response in a delay (500-ms conditioned stimulus [CS], 400-ms interstimulus interval [ISI]), long-delay (1,000-ms CS, 900-ms ISI), or trace (500-ms CS, 400-ms stimulus-free period) paradigm. Collapsing across age groups, there is a general tendency for animals to acquire trace conditioning more slowly than delay conditioning. Collapsing across conditioning paradigms, there is a general tendency for aged animals to acquire more slowly than younger animals. Of greater significance, however, are the age differences in the different conditioning paradigms. In the delay and long-delay paradigms, significant conditioning deficits first appeared in the 4(+)-year-old group. In the trace conditioning paradigm, significant conditioning deficits became apparent in the 2(+)-year-old animals.

Interaction of tail-pressure stress and d-amphetamine in disruption of the rat's ability to ignore an irrevelant stimulus.

Rats received either 0 or 30 preexposures to a tone that was later used as a warning stimulus in a two-way active avoidance task. Consistent with previous data, tone preexposure resulted in retarded acquisition of the conditioned avoidance response (CAR) in saline control animals and in animals that received chronic administration of a low dose of d-amphetamine. Similarly, animals that received tail-pressure stress prior to stimulus preexposure also showed retarded acquisition of the CAR. However, animals that received a combination of tail pressure and d-amphetamine did not show retarded CAR acquisition following stimulus preexposure. These results suggest an interaction between environmental stressors and d-amphetamine in producing attentional deficits.

Lesions of the middle cerebellar peduncle disrupt acquisition and retention of the rabbit's classically conditioned nictitating membrane response.

Rabbits were classically conditioned to emit a nictitating membrane response (NMR) to either a light or tone conditioned stimulus (CS) paired with an eye shock unconditioned stimulus (UCS). They then received lesions of the middle cerebellar peduncle (MCP) or served as unoperated controls. Following surgery, they were given separate presentations of tone, light, and vibratory CSs, each paired with the eye shock UCS. In this way, conditioned responses (CR) to the previously trained light or tone served as a test of retention, whereas CRs to the remaining two conditioned stimuli (tone and vibratory or light and vibratory) served as a test of acquisition. The results of the study revealed that rabbits with complete lesions of the MCP showed disrupted acquisition and retention of the conditioned NMR to all stimuli, rabbits with partial MCP lesions also showed disrupted acquisition and retention to all CSs, but to a lesser degree, and animals with lesions that missed the MCP and unoperated controls both showed normal acquisition and retention of the conditioned NMR. These data are consistent with the view that the cerebellum is an essential part of the circuit for classical conditioning of the NM response and that information about CSs in the auditory, visual, and tactile modalities reach the cerebellum by way of the MCP.

Disrupted eyelid conditioning in a patient with damage to cerebellar afferents.

A 54-year-old woman with damage to cerebellar circuitry resulting from a cerebrovascular accident underwent classical conditioning of the eye-blink response to a tone conditioned stimulus and an air-puff unconditioned stimulus. In contrast to 5 age-matched controls who readily acquired the conditioned response (CR), emitting a mean of 56.7 CRs over 70 trials, the patient emitted only 6 CRs in 100 trials and never emitted 2 consecutive CRs. There were no differences in spontaneous blink rate, sensitivity to the air puff, or sensitivity to the tone between the experimental subject and the control subjects. That conditioning of the eye-blink response is disrupted in a human with damage to cerebellar circuitry is consistent with an accumulating body of literature indicating that the cerebellum is the essential site of plasticity for classically conditioned somatic responses.