Alcohol Effects on Information Processing Time with an Overlearned Task1

Response latencies in naming visually displayed numbers were measured for 20 Ss under control and alcohol treatments. The size of the stimulus pool was varied by sets of trials to produce stimulus-response uncertainty in the range 0 to 5 bits. Response latencies were a function of the amount of uncertainty, but alcohol impairment was not.

N-acetyl cysteine reverses bio-behavioural changes induced by prenatal inflammation, adolescent methamphetamine exposure and combined challenges

RATIONALE

Schizophrenia is associated with prenatal inflammation and/or postnatal stressors such as drug abuse, resulting in immune-redox dysfunction. Antioxidants may offer therapeutic benefits.

OBJECTIVES

The objective of this study is to investigate N-acetyl cysteine (NAC) as a therapeutic antioxidant to reverse schizophrenia-like bio-behavioural changes in rats exposed to maternal immune activation (MIA), adolescent methamphetamine (MA) or a combination thereof.

METHODS

Sprague-Dawley offspring prenatally exposed to saline/lipopolysaccharide (LPS) received saline or MA (0.2-6 mg kg^-1 twice daily × 16 days) during adolescence and divided into LPS, MA and LPS + MA groups. Vehicle/NAC (150 mg kg^-1 × 14 days) was administered following MA/saline exposure on postnatal day 51-64. Social interaction, novel object recognition and prepulse inhibition (PPI) of startle, as well as regional brain monoamines, lipid peroxidation, plasma reactive oxygen species (ROS) and pro- and anti-inflammatory cytokines (TNF-α; IL-10), were assessed.

RESULTS

NAC reversed LPS, MA and LPS + MA-induced anxiety-like social withdrawal behaviours, as well as MA and LPS + MA-induced deficits in recognition memory. PPI deficits were evident in MA, LPS and LPS + MA models, with NAC reversing that following LPS + MA. NAC reversed LPS, MA and LPS + MA-induced frontal cortical dopamine (DA) and noradrenaline (NA) elevations, LPS and LPS + MA-induced frontal cortical 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and striatal NA deficits as well as LPS + MA-induced frontal cortical 5-HT turnover. Decreased IL-10 in the LPS, MA and LPS + MA animals, and increased TNF-α in the LPS and MA animals, was reversed with NAC. NAC also reversed elevated lipid peroxidation and ROS in the LPS and LPS + MA animals.

CONCLUSIONS

Prenatal LPS, LPS + postnatal MA challenge during adolescence, and to a lesser extent MA alone, promotes schizophrenia-like bio-behavioural changes later in life that are reversed by NAC, emphasizing therapeutic potential for schizophrenia and MA-associated psychosis. The nature and timing of the dual-hit are critical.

Wnt signaling in form deprivation myopia of the mice retina

BACKGROUND

The canonical Wnt signaling pathway plays important roles in cellular proliferation and differentiation, axonal outgrowth, cellular maintenance in retinas. Here we test the hypothesis that elements of the Wnt signaling pathway are involved in the regulation of eye growth and prevention of myopia, in the mouse form-deprivation myopia model.

METHODOLOGY/PRINCIPAL FINDINGS

(1) One hundred twenty-five C57BL/6 mice were randomly distributed into form-deprivation myopia and control groups. Form-deprivation myopia (FDM) was induced by suturing the right eyelid, while the control group received no treatment. After 1, 2, and 4 weeks of treatment, eyes were assessed in vivo by cycloplegic retinoscopic refraction and axial length measurement by photography or A-scan ultrasonography. Levels of retinal Wnt2b, Fzd5 and β-catenin mRNA and protein were evaluated using RT-PCR and western blotting, respectively. (2) Another 96 mice were divided into three groups: control, drugs-only, and drugs+FDM (by diffuser). Experimentally treated eyes in the last two groups received intravitreal injections of vehicle or the proteins, DKK-1 (Wnt-pathway antagonist) or Norrin (Wnt-pathway agonist), once every three days, for 4 injections total. Axial length and retinoscopic refraction were measured on the 14th day of form deprivation. Following form-deprivation for 1, 2, and 4 weeks, FDM eyes had a relatively myopic refractive error, compared with contralateral eyes. There were no significant differences in refractive error between right and left eye in control group. The amounts of Wnt2b, Fzd5 and β-catenin mRNA and protein were significantly greater in form-deprived myopia eyes than in control eyes.DKK-1 (antagonist) reduced the myopic shift in refractive error and increase in axial elongation, whereas Norrin had the opposite effect in FDM eyes.

CONCLUSIONS/SIGNIFICANCE

Our studies provide the first evidence that the Wnt2b signaling pathway may play a role in the development and progression of form-deprivation myopia, in a mammalian model.

Chronic oral methylphenidate administration to periadolescent rats yields prolonged impairment of memory for objects

Methylphenidate (MPD) is widely prescribed for the treatment of attention deficit disorders in children and has generally been thought to be free of significant side effects when administered at recommended therapeutic doses. However, recent behavioral research with laboratory rodents has indicated that, like other psychostimulants with which it shares neurotransmitter-modulating properties, chronically administered MPD can bring about lasting and potentially detrimental alterations in brain function. Some of these may involve changes in the neuromodulatory input from noradrenergic and dopaminergic systems that project to the prefrontal cortex and hippocampus, regions with significant roles in several cognitive functions, including those critical to memory formation. To investigate the possibility of cognitive impairment, the effects of a regimen of chronic MPD on the performance of an object recognition task known to rely on the integrity of systems involved in rodent memory was assessed. The drug, at doses of 2, 3 or 5mg/kg, was delivered twice daily to periadolescent rats via an oral administration technique on either 11 or 21 treatment days. Subsequent to this period, the animals were subjected to an object recognition test at 14, 28, and 42 days after their last MPD treatment. In each of these tests, exploration time for two objects, one novel and one previously encountered (3h earlier), was assessed. Longer exploration of the novel object was considered evidence of retained memory for the familiar object. It was found that rats exposed to 3 or 5mg/kg (b.i.d.) on 21 occasions exhibited no significant preference for exploration of the novel object at any of the three post-treatment intervals. This finding was interpreted as evidence of a persisting MPD-induced impairment of recognition memory in these animals.

NMDA receptor modulation by D-cycloserine promotes episodic-like memory in mice

RATIONALE

NMDA-R (N-methyl-D-aspartate receptors) have been implicated in synaptic plasticity underlying one-trial learning of event-place associations. In rodents, episodic-like memory (ELM) of personally experienced events can be inferred from behavior that reflects the remembrance of the content (what kind of object was presented), place (where was this object placed), and temporal context (when was the object presented). We have previously shown that that D-cycloserine (DCS), an NMDA-R agonist, ameliorates stress-induced deficits in ELM.

OBJECTIVES

In this study, we used an experimental protocol designed to detect promnestic drug effects and investigated whether DCS, which is known to enhance learning and memory, can induce ELM under conditions where mice normally do not show ELM.

RESULTS

Mice that have been treated i.p. with DCS (20 mg/kg) both remembered the temporal order in which two different objects had been encountered during two consecutive sample trials, as well as their spatial position during the sample trials. Most importantly, the test trial performance of these mice is compatible with ELM in terms of an integrated memory for unique experiences comprising "what", "where", and "when" information. In contrast, mice that have received either a saline injection or lower doses of DCS (0.2 and 2.0 mg/kg) did not show such an integrated ELM.

CONCLUSIONS

To our knowledge, this is the first report showing that DCS can promote ELM in mice.

The effect of chronic peripubertal cannabinoid treatment on deficient object recognition memory in rats after neonatal mPFC lesion

We here report on behavioral effects of neonatal medial prefrontal cortex (mpfc) lesions in rats, followed by chronic peripubertal treatment with the cannabinoid full agonist WIN 55,212-2 (WIN). Rat pups received excitotoxic lesions of the mpfc on postnatal day (pd) 7. Chronic WIN (1.2 mg/kg) treatment was extended throughout the rats' puberty (pd 40-65). All animals were tested as juveniles and adults for short-term memory functioning using the spontaneous object recognition test, and for locomotor activity in an open field. Lesioned rats showed impairments in recognition memory when tested prepubertally. Postpubertal testing of lesioned animals revealed a persisting recognition memory impairment that was intensified by pubertal WIN treatment. Chronic WIN treatment during puberty also affected recognition memory in sham-lesioned rats and controls. No effects on locomotor activity of either neonatal lesion or pubertal cannabinoid treatment were found. This study shows that behavioral deviations induced by neonatal mPFC lesions can be exacerbated by pubertal chronic cannabinoid treatment, leading to long-lasting impairments of mnemonic short-term information processing.

Recognition of category-related visual stimuli in Parkinson's disease: Before and after pharmacological treatment

Visual-sensory dysfunctions and semantic processing impairments are widely reported in Parkinson's disease (PD) research. The present study investigated the category-specific deficit in object recognition as a function of both the semantic category and spatial frequency content of stimuli. In the first experiment, the role of dopamine in object-recognition processing was assessed by comparing PD drug naïve (PD-DN), PD receiving levodopa treatment (PD-LD), and control subjects. Experiment 2 consisted of a retest session for PD drug naïve subjects after a period of pharmacological treatment. All participants completed an identification task which displayed animals and tools at nine levels of filtering. Each object was revealed in a sequence of frames whereby the object was presented at increasingly less-filtered images up to a complete version of the image. Results indicate an impaired identification pattern for PD-DN subjects solely for animal category stimuli. This differential pharmacological therapy effect was also confirmed at retest (experiment 2). Thus, our data suggest that dopaminergic loss has a specific role in category-specific impairment. Two possible hypotheses are discussed that may account for the defective recognition of semantically different objects in PD.

Effects of a neurotensin analogue (PD149163) and antagonist (SR142948A) on the scopolamine-induced deficits in a novel object discrimination task

Various lines of evidence suggest a role in cognition for the endogenous neuropeptide, neurotensin, involving an interaction with the central nervous system cholinergic pathways. A preliminary study has shown that central administration of neurotensin enhances spatial and nonspatial working memory in the presence of scopolamine, a muscarinic receptor antagonist which induces memory deficits. Utilizing similar methods, the present study employed a two-trial novel object discrimination task to determine the acute effect of a neurotensin peptide analogue with improved metabolic stability, PD149163, on recognition memory in Lister hooded rats. Consistent with previous findings with neurotensin, animals receiving an intracerebroventricular injection of PD149163 (3 microg) significantly discriminated the novel from familiar object during the choice trial. In addition, a similar dose of PD149163 restored the scopolamine-induced deficit in novelty recognition. The restoration effect on scopolamine-induced amnesia produced by PD149163 was blocked by SR142948A, a nonselective neurotensin receptor antagonist, at a dose of 1 mg/kg (intraperitonial) but not at 0.1 mg/kg. In conclusion, the present results confirm a role for neurotensin in mediating memory processes, possibly via central cholinergic mechanisms.

Immune activation during pregnancy in mice leads to dopaminergic hyperfunction and cognitive impairment in the offspring: a neurodevelopmental animal model of schizophrenia

BACKGROUND

Maternal viral infection is associated with increased risk for schizophrenia. It is hypothesized that the maternal immune response to viruses may influence fetal brain development and lead to schizophrenia.

METHODS

To mimic a viral infection, the synthetic double strand RNA polyriboinosinic-polyribocytidilic acid (poly I:C) was administered into pregnant mice. Behavioral evaluations (thigmotaxis, methamphetamine [MAP]-induced hyperactivity, novel-object recognition test [NORT]), sensorimotor gating (prepulse inhibition [PPI]), and biochemical evaluation of the dopaminergic function of the offspring of phosphate-buffered saline (PBS)-treated dams (PBS-mice) and that of poly I:C-treated dams (poly I:C-mice) were examined.

RESULTS

In juveniles, no difference was found between the poly I:C-mice and PBS-mice. However, in adults, the poly I:C-mice exhibited attenuated thigmotaxis, greater response in MAP-induced (2 mg/kg) hyperlocomotion, deficits in PPI, and cognitive impairment in NORT compared with the PBS-mice. Cognitive impairment in the adult poly I:C-mice could be improved by subchronic administration of clozapine (5.0 mg/kg) but not haloperidol (.1 mg/kg). Increased dopamine (DA) turnover and decreased receptor binding of D2-like receptors, but not D1-like receptors, in the striatum were found in adult poly I:C-mice.

CONCLUSIONS

Prenatal poly I:C administration causes maturation-dependent increased subcortical DA function and cognitive impairment in the offspring, indicating a neurodevelopmental animal model of schizophrenia.

The selective PDE5 inhibitor, sildenafil, improves object memory in Swiss mice and increases cGMP levels in hippocampal slices

Previous studies have shown memory enhancing effects of phosphodiesterase type 5 (PDE5) inhibitors in rats. However, differences in nitric oxide (NO)-mediated cyclic GMP (cGMP) signaling in the hippocampus have been described between rats and mice. In the present study we investigated the memory enhancing effects of the PDE5 inhibitor, sildenafil on memory performance in Swiss mice using the object recognition task. Sildenafil (0.3, 1 and 3 mg/kg) was administered orally directly after the first trial. The memory for the objects was retested 24 h later when mice show no memory for the familiar object. Sildenafil improved the object discrimination performance of Swiss mice at a dose of 1 mg/kg. Hippocampal slices of Swiss mice incubated with sildenafil (10 microM) increased cGMP levels in varicosities in the CA3 region of the hippocampus and a number of short, thin fibers. Addition of DEA/NO, an NO donor (10 microM), in the presence of sildenafil (10 microM) strongly increased cGMP immunoreactivity of varicosities in the CA3 region. Double immunostaining of cGMP with the presynaptic marker synaptophysin did not reveal any co-localization of these markers under any circumstance. Taken together, inhibition of PDE5 improves object recognition memory in mice. Furthermore, a postsynaptic role of cGMP could be involved in this respect.

Prenatal cocaine exposure specifically alters spontaneous alternation behavior

Our laboratory has previously characterized a rabbit model of gestational cocaine exposure in which permanent alterations in neuronal morphology, cell signaling and psychostimulant-induced behavior are observed. The cellular and molecular neuroadaptations produced by prenatal cocaine occur in brain regions involved in executive function and attention, such as the anterior cingulate and medial prefrontal cortices. Therefore, in the present study, we have measured the effects of prenatal cocaine exposure on specific behavioral tasks in adult offspring whose mothers were treated with cocaine (3mg/kg, twice a day, E16-E25). We assessed non-spatial, short-term memory in a two-object recognition task and found no deficits in memory or exploratory behaviors in cocaine-exposed offspring in this paradigm. We also evaluated a different memory task with a more robust attentional component, using spontaneous alternation in a Y maze. In this task, young adult rabbits exposed to cocaine prenatally exhibited a significant deficit in performance. Deficits in spontaneous alternation can be induced by a wide variety of behavioral and cognitive dysfunctions, but taken together with previous findings in this and other animal models, we hypothesize that prenatal exposure to cocaine alters highly specific aspects of cognitive and emotional development.

On the delay-dependent involvement of the hippocampus in object recognition memory

The role of the hippocampus in object recognition memory processes is unclear in the current literature. Conflicting results have been found in lesion studies of both primates and rodents. Procedural differences between studies, such as retention interval, may explain these discrepancies. In the present study, acute lidocaine administration was used to temporarily inactivate the hippocampus prior to training in the spontaneous object recognition task. Male C57BL/6J mice were administered bilateral lidocaine (4%, 0.5 microl/side) or aCSF (0.5 microl/side) directly into the CA1 region of the dorsal hippocampus 5 min prior to sample object training, and object recognition memory was tested after a short ( 5 min) or long (24 h) retention interval. There was no effect of intra-hippocampal lidocaine on the time needed for mice to accumulate sample object exploration, suggesting that inactivation of the hippocampus did not affect sample session activity or the motivation to explore objects. Lidocaine-treated mice exhibited impaired object recognition memory, measured as reduced novel object preference, after a 24 h but not a 5 min retention interval. These data support a delay-dependent role for the hippocampus in object recognition memory, an effect consistent with the results of hippocampal lesion studies conducted in rats. However, these data are also consistent with the view that the hippocampus is involved in object recognition memory regardless of retention interval, and that object recognition processes of parahippocampal structures (e.g., perirhinal cortex) are sufficient to support object recognition memory over short retention intervals.

Impaired performance of children exposed in utero to cocaine on a novel test of visuospatial working memory

The present study examines the potentially harmful effects of prenatal cocaine exposure on later visuospatial memory functions. A novel neuropsychological measure of immediate- and short-term memory for visuospatial information was administered to 40 children, who were identified as cocaine-exposed, and 11 age and socioeconomic status matched controls (all children were 8-9 years old). The Groton Maze Learning Test is a computer-based hidden maze learning test that consists of a 'timed chase test' (a simple measure of visuomotor speed), 5 learning trials on a hidden maze, followed by a delayed recall trial after an 8 min delay. The specific test parameters are chosen based on the age cohort of the subjects. The cocaine-exposed group performed significantly slower on the 'timed chase test,' the last 3 learning trials, and the delayed recall trial (p < or = .05 for all comparisons). Although there was a modest trend for the cocaine-exposed group to make more errors throughout the learning trials, there were no significant group differences. These results suggest that children who were exposed in utero to cocaine exhibit slowed visuomotor speed, a possible impairment in procedural learning, and diminished efficiency in accessing and using the internal spatial map that subjects create to master the maze.

Moderate alcohol consumption in humans impairs feature binding in visual perception but not across perception and action

Animal studies suggest a relationship between activation of the cholinergic system and neural synchronization, which again has been suggested to mediate feature binding. We investigated whether suppressing cholinergic activity through moderate alcohol consumption in healthy humans affects behavioral measures of feature binding in visual perception and across perception and action. Indeed, evidence of the binding of shape and color, and of shape and location, of visual objects disappeared after alcohol consumption, whereas bindings between object features and the manual response were unaffected.

Effects of intra-accumbens focal administrations of glutamate antagonists on object recognition memory in mice

Generally recognition memory is distinguished into spatial and object memories that have been suggested to relay at a cortical level on different neural substrates. Recent studies point to a possible involvement of the nucleus accumbens (Nac) in spatial memory, demonstrating that blockade of glutamate antagonists within this structure impairs acquisition and consolidation of spatial information, while not many data are available on the potential role of this structure in object recognition. Thus in this study we wanted to investigate the effects of intra-accumbens focal administrations of NMDA antagonist, AP-5 (0.05, 0.1, 0.15 or 0.2 microg per side), and AMPA antagonist, DNQX (0.0005 or 0.001 microg per side), in object recognition memory. The spontaneous preference displayed by mice for novel objects was taken as an index for measuring object recognition. Pre-training focal administrations of both antagonists impaired the ability of mice to selectively explore the novel object in test session. However, the AMPA antagonist induced also a decrease in exploration and locomotion. In order to assess whether glutamate receptors located within the Nac were also involved in subsequent steps of object information processing, we performed additional experiments injecting AP-5 and DNQX immediately after training and testing the animals 24-h later. In this case, AP-5 but not the AMPA antagonist impaired exploration of the novel object. These results demonstrate that the Nac is involved in object recognition, and confirm that the different glutamate receptors mediate different component of information processing within the accumbens.

Effect of benzodiazepines on structural and conceptual/lexical priming

RATIONALE

Impaired perceptual priming, as assessed by naming reaction times and accuracy, for briefly presented contour-deleted pictures under lorazepam has been documented in several studies but whether the nature of this impairment is visual versus conceptual/lexical is not clear. We used a previously developed paradigm to examine whether lorazepam affects visual processes involved in the coding of contour information or conceptual/lexical representations.

METHOD

Three groups were tested (lorazepam, diazepam and placebo). In the study phase, participants named line drawings, presented for 500 ms, in which 50% of the contour was deleted by removing every other line and vertex from each part. In the test phase, participants saw the identical picture, its complement (the other 50% of the contour), or a samename/different-shape picture, each presented for 200 ms.

RESULTS

For all three groups, the magnitude of priming, as assessed by naming RTs and error rates, was equivalent in the identical and in the complementary conditions and the amount of facilitation was reduced in the same-name condition. Perceptual priming occurred both in the lorazepam and in the diazepam groups, though reduced, compared to placebo, for RTs. No conceptual priming (i.e. facilitated performance in the same-name condition) was observed in the benzodiazepine groups.

CONCLUSION

Equivalent priming for identical and complementary pictures in the three groups suggests that benzodiazepines do not affect the activation of the geon structural description. The lack of priming for same-name pictures suggests that benzodiazepines affect access, retrieval or selection of conceptual/lexical information.

Small conductance Ca2+-activated K+ channels modulate synaptic plasticity and memory encoding

Activity-dependent changes in neuronal excitability and synaptic strength are thought to underlie memory encoding. In hippocampal CA1 neurons, small conductance Ca2+-activated K+ (SK) channels contribute to the afterhyperpolarization, affecting neuronal excitability. In the present study, we examined the effect of apamin-sensitive SK channels on the induction of hippocampal synaptic plasticity in response to a range of stimulation frequencies. In addition, the role of apamin-sensitive SK channels on hippocampal-dependent memory encoding and retention was also tested. The results show that blocking SK channels with apamin increased the excitability of hippocampal neurons and facilitated the induction of synaptic plasticity by shifting the modification threshold to lower frequencies. This facilitation was NMDA receptor (NMDAR) dependent and appeared to be postsynaptic. Mice treated with apamin demonstrated accelerated hippocampal-dependent spatial and nonspatial memory encoding. They required fewer trials to learn the location of a hidden platform in the Morris water maze and less time to encode object memory in an object-recognition task compared with saline-treated mice. Apamin did not influence long-term retention of spatial or nonspatial memory. These data support a role for SK channels in the modulation of hippocampal synaptic plasticity and hippocampal-dependent memory encoding.

Memory impairment following combined exposure to delta(9)-tetrahydrocannabinol and ethanol in rats

Cannabis derivatives and alcohol are widely co-abused, particularly among adolescents. Since both ethanol and cannabinoids are known to impair learning and memory, the present study investigated in rats the effects of combined exposure to ethanol and delta(9)-tetrahydrocannabinol (THC) in a memory task, the object recognition test. The results of the present study provide evidence that ethanol, voluntarily ingested in alcohol-preferring rats, and THC, given by intraperitoneal injection, have a synergic action to impair object recognition, when a 15-min interval was adopted between the sample phase and the choice phase of the test. Neither voluntary ethanol ingestion nor 2 or 5 mg/kg of THC were able per se to modify object recognition in these experimental conditions, but when voluntary ethanol ingestion was combined with administration of these doses of THC object recognition was markedly impaired. THC impaired object recognition only at the dose of 10 mg/kg, when its administration was not combined with that of ethanol. The selective cannabinoid CB(1) receptor antagonist SR 141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1(2, 4-dichloro-phenyl)-4-methyl-1H-pyrazole carboxamide.HCl) at the dose of 1 mg/kg reversed the amnesic effect of THC, 10 mg/kg, suggesting that the effect is mediated by this receptor subtype. The synergism of ethanol and THC was not detected when an inter-trial interval of 1 min was adopted. The present findings are in keeping with the notion that Cannabis derivatives impair memory processes and provide evidence for a synergic action of THC and ethanol, thus emphasizing the risks consequent to their co-administration.

Nimodipine prevents scopolamine-induced impairments in object recognition

The effects of acute administration of the dihydropyridine calcium channel antagonist, nimodipine, were studied on the actions of scopolamine in the object recognition test. Scopolamine at 0.125 mg/kg decreased the difference in the time spent exploring novel and familiar objects when given either 15 min before, or immediately after, exposure to objects. Administration of nimodipine at 10 mg/kg, or 1 mg/kg, at the same time as the scopolamine completely prevented the deleterious effects on memory in this task. This effect was seen when nimodipine and/or scopolamine were given prior to the object exposure and also when the drugs were given after the experience of seeing the objects. Nimodipine had no effects on performance when given in the absence of scopolamine. This lack of change in total time spent exploring the objects indicated that the effects of scopolamine and nimodipine were not due to changes in motor coordination or alertness. The results are discussed in the light of the role of cholinergic transmission in memory and the known actions of dihydropyridines on brain function.

Estrogen effects on object memory and cholinergic receptors in young and old female mice

We investigated whether object recognition memory is modulated by estrogen in young (5 month) and aged (24 month) female C57Bl/6J mice, and if cholinergic muscarinic receptors might contribute to this response. Mice that were ovariectomized, or ovariectomized plus estradiol-treated three weeks before behavioral testing or quantitative autoradiography were compared to intact mice. Memory for a previously encountered object deteriorated significantly between 3 and 6h after initial exposure, regardless of animal age. In both young and aged mice, estradiol-treated mice showed significantly greater recall than did ovariectomized mice. In both age groups, the apparent number of [(3)H]pirenzepine/M(1)-like and [(3)H]AFDX384/M(2)-like muscarinic receptor binding sites was reduced in the basal forebrain as well as its projection areas following ovariectomy, but this decrease was not alleviated by estrogen. Aging poorly affected object memory, but reduced muscarinic binding in some cortical subregions and in the caudate nucleus. These findings suggest that estrogen effects on memory in C57Bl/6J mice are not due to changes in the number of muscarinic receptors.

Dopaminergic and cholinergic antagonism in a novel-object detection task with rats

In a free-choice test, rats display a tendency to interact more with a novel object than a familiar object. In the present report, we assessed the role of the dopaminergic and cholinergic systems in the expression of this novelty detection. Rats were injected with a dopaminergic antagonist (sulpiride, U-99194A, clozapine, or L-745,870) or a cholinergic antagonist (mecamylamine or scopolamine) prior to the free-choice novel-object test. The dopamine antagonists did not block novel-object detection. In contrast, scopolamine, but not mecamylamine, reliably blocked the expression of novelty detection, indicating a role for muscarinic receptors.

Influence of hypoglycaemia, with or without caffeine ingestion, on visual sensation and performance

Full-field visual evoked potentials and visual information processing were measured in 16 normal, healthy subjects during a hyperinsulinaemic clamp. A randomized cross-over design was used across three conditions: hypoglycaemia and caffeine; hypoglycaemia and placebo; and euglycaemia and caffeine. The latency of the P100 component of the pattern-reversal visual evoked potential increased significantly from rest to hypoglycaemia, but no effect of caffeine was found. Subjects were subsequently divided into two median groups based on the increase in P100 latency in the placebo condition (Group 1, +0.5 ms; Group 2, +5.6 ms). In the absence of caffeine, an inverse correlation between the increase in P100 latency from rest and a deterioration in visual movement detection was found for Group 2, but not for Group 1. Caffeine ingestion resulted in a further increase in P100 latency, from rest to hypoglycaemia, for subjects in Group 2. Hypoglycaemia in the absence of caffeine produces changes in visual sensation from rest to hypoglycaemia. In those subjects most sensitive to the effects of hypoglycaemia (Group 2), the increase in P100 latency was associated with poorer performance in tests of visual information processing. Caffeine ingestion produced further increases in P100 latency in these subjects.

Scopolamine-induced impairment of delayed recognition of abstract visual shapes

Since the limbic system, whose involvement in cognitive processes is well documented, constitutes a major central cholinergic area, the effect of cholinergic drugs on cognitive tasks has been studied extensively. In the present study, we used a long-term visual recognition task to evaluate the persistence of the scopolamine-induced anterograde amnesia beyond drug clearance intervals. Following memorization of a list of abstract shapes, subjects were evaluated on recognition performance immediately after encoding, and after a 3-day interval. Administration of scopolamine (0.4-0.8 mg) 70 min prior to encoding induced a significant (8-16%) deficit in delayed recognition performance. In contrast, a scopolamine challenge on delayed recognition following a drug-free encoding did not influence memory performance. In contrast, even at peak levels, scopolamine did not alter immediate recognition, detection or visual discriminative performances. Hence, the presence of scopolamine during the encoding of the shapes induced a significant long-term memory deficit that persisted after scopolamine clearance. Therefore, this paradigm is useful for imaging regional brain activation during impaired recognition without the confounding direct effects of scopolamine on cerebral blood flow or metabolism, two physiological variables underlying the indirect measurement of brain activation.

Effects of neurotrophins on cortical plasticity: same or different?

Neurotrophins are important regulators of visual cortical plasticity. It is still unclear, however, whether they play similar or different roles and which are their effects on the electrical activity of cortical neurons in vivo. We therefore compared the effects of all neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4), and neurotrophin-3 (NT-3) on visual cortical plasticity and on cell spontaneous and visually evoked activity. Rats were monocularly deprived for 1 week at the peak of the critical period, and neurotrophins were infused intracortically. The main finding is that, with the exception of NT-3, all neurotrophins affect the outcome of monocular deprivation, but there are clear differences in their mechanisms of action. In particular, NT-4 and NGF counteract monocular deprivation effects without causing detectable alterations either in spontaneous or visually evoked neuronal activity. BDNF is less effective on ocular dominance plasticity and, in addition, strongly affects spontaneous and visually evoked activity in cortical neurons.

Specific characteristics of cholinergic mechanisms of short-term memory in monkeys for different types of visual information: the effects of amizil

Experiments on rhesus macaques were used to study the relationship between the characteristics of delayed visual differentiation and stimulus properties in conditions of pharmacological treatment with the m-cholinoreceptor blocker amizil, with the aim of identifying how modification of cholinergic structures affects different types of information. Disturbances to short-term memory for all stimuli consisted of reductions in the duration of retention and increases in motor reaction times, but occurred at different doses of the blocker: amizil at a dose of 0.3 mg/kg significantly decreased the retention duration for information relating to spatial relationships. Delayed discrimination of shape, contrast, and size worsened after treatment with amizil at a dose of 0.45-0.50 mg/kg, while decreases in the duration of short-term storage of information relating to color started after amizil doses of 0.6-0.8 mg/kg. It is suggested that the short-term memory system includes a set of neurophysiological mechanisms in which the cholinergic structures are organized differently and whose specific properties result in differences in the characteristics of short-term storage of different types of visual information.

Effects of alcohol on perceptual speed

In moderate to heavy doses, alcohol adversely affects performance on many tasks, and perceptual speed is a component in most performance tasks. Nevertheless, studies of alcohol's effects on perceptual speed have been largely limited to critical flicker frequency and backward masking. The present study extends these limits. 16 men and 12 women were administered four temporal-factors tests before and after the ingestion of alcohol. The four tests were Simultaneity, Apparent Movement, Bistable Stroboscopic Motion, and Backward Masking. At the first postalcohol testing (mean BAC = 0.111), all four tests showed pre-posttest changes indicating slowed perceptual speed. Perceptual speed was still slowed when BAC decreased to .096. When mean BAC decreased to .076, however, only Simultaneity and Backward Masking were still significantly slowed. At moderate BACs and possibly at lower ones, the effects of alcohol on task performance appear to be mediated in part by slowed perceptual speed.

[Short-term memory processes during delayed visual differentiation after bilateral removal of the 7th field of the parietal cortex in Rhesus macaca]

Extirpation of the parietal cortex area 7 aggravated delayed visual discrimination of all visual attributes including shape, colour and spatial relationship in adult rhesus monkeys. Oxymetacil improved the shape and colour discrimination alone.

Occupational exposure to lead and neuropsychological dysfunction

OBJECTIVE

To evaluate the neuropsychological effects of current low level and previous higher levels of exposure to lead and evaluate the relation between effects of lead and bone lead.

METHODS

A neuropsychological test battery was given to 54 storage battery workers with well documented long term exposure to lead. The effect was studied in two subgroups: those whose blood lead had never exceeded 2.4 mmol/l (the low BPbmax group, n = 26), and those with higher exposure about 10 years earlier (the high BPbmax group, n = 28). In both groups, the recent exposure had been low. Correlations between the test scores and the indices of both long term and recent exposure--including the content of lead in the tibial and calcaneal bone--and covariance analyses were used to assess the exposure-effect relation. Age, sex, and education were controlled in these analyses.

RESULTS

Analyses within the low BPbmax group showed a decrement in visuospatial and visuomotor function (block design, memory for design, Santa Ana dexterity), attention (digit symbol, digit span), and verbal comprehension (similarities) associated with exposure to lead and also an increased reporting of subjective symptoms. The performance of the high BPbmax group was worse than that of the low BPbmax group for digit symbol, memory for design, and embedded figures, but there was no reporting of symptoms related to exposure, probably due to selection in this group. No relation was found between the output variables and the tibial lead concentration. The calcaneal lead concentrations were related to the symptoms in the low BPbmax group.

CONCLUSIONS

Neuropsychological decrements found in subjects with high past and low present exposure indicate that blood lead concentrations rising to 2.5-4.9 mmol/l cause a risk of long lasting or even permanent impairment of central nervous system function. Milder and narrower effects are associated with lower exposures; their reversibility and time course remain to be investigated. History of blood lead gives a more accurate prediction of the neuropsychological effects of lead than do measurements of bone lead.

Asymmetries in the effect of side of seizure onset on recognition memory following intracarotid amobarbital injection

PURPOSE

To assess interhemispheric differences in recognition memory for objects during the intracarotid amobarbital sodium procedure (IAP).

METHODS

The recognition memory for real objects of patients with either right (RTLE; n = 28) or left (LTLE; n = 22) temporal lobe epilepsy was assessed at baseline, and after left and right intracarotid amobarbital sodium injection.

RESULTS

There were no differences between groups on baseline performance. Performance following injection ipsilateral to the side of seizure focus was relatively lower for the LTLE as compared with the RTLE group, but this difference did not reach statistical significance. However, performance following injection contralateral to the side of seizure focus was significantly lower for the RTLE as compared with the LTLE group. Within-group differences in performance after ipsilateral as compared with contralateral injection were significant for the RTLE but not the LTLE group. The difference in interhemispheric asymmetry in IAP memory performance between RTLE and LTLE groups was reflected in decreased ability to classify LTLE patients as compared with RTLE patients about side of seizure onset, using a clinically applicable decision rule.

CONCLUSIONS

Recognition memory during the IAP for real objects, simultaneously named and presented visually during encoding, is mediated effectively by both the left and right hemisphere when there is no seizure focus present. However, memory appears to be more vulnerable to the presence of a seizure focus in the right as compared with the left hemisphere.

The effect of naloxone on object exploration, object recognition and other types of spontaneous behavior

Object exploration was examined in naloxone injected (1 mg/kg or 4 mg/kg) and saline control rats. Naloxone rats explored an object for a shorter time than did controls, thus indicating a lower investigatory motivation. This effect was dose dependent. Higher drug dose (4 mg/kg) decreased the number of contacts with an object. Both doses increased the mean duration of contacts with an object. The naloxone groups showed intact recognition of a familiar object paired with a new one in two sessions--4 h and 24 h after the injections. The higher drug dose depressed the locomotor activity and wall leaning. Grooming was not influenced by naloxone. The normal daily fluctuations in the level of grooming and locomotion were distorted following the injection of the higher dose of naloxone. The lower dose (1 mg/kg) did not affect the rats' performance in some tests. The results could be viewed as a naloxone-related depression of the behavior containing motor elements like locomotion, wall leaning and object approaching. The prolonged contact time with an object could be the result of a lowered flexibility of movement. However, the decrease of rewarding value of exploration could not be ruled out. Possibly, naloxone exerts several different interacting behavioral effects.

Lorazepam impairs perceptual integration of visual forms: a central effect

Previous studies have shown a lorazepam effect on visual perception. We tested whether this impairment resulted from a peripheral effect induced by benzodiazepines. A first experiment showed that a single dose of lorazepam induces an oculomotor imbalance without impairing visual acuity or accommodation. In a second experiment, we tested whether the impairment induced by lorazepam on visual perception still occurred in monocular vision. Subjects matched incomplete forms controlled on the spacing and alignment of their local contour elements. A reference object was first displayed and followed by two laterally displayed objects, a target and a distractor. The distractor was the mirror-reversed version of the target. Performance was impaired in the lorazepam group when the reference was an incomplete form with a spacing of 10.8' or 22.2' of arc. These results were not correlated with sedation. They confirm that lorazepam has a central deleterious effect on visual perception. A post-hoc analysis also suggested that lorazepam-treated subjects used asymmetry in the stimuli as a compensatory strategy. This result is discussed in relation to previous hypotheses about the physiological mechanisms that determine the effects of lorazepam on visual perception.

Effects of caffeine on functional asymmetry in a Posner letter-recognition task

A Posner task was used to investigate whether caffeine, in common with other drugs, has an asymmetric effect on cerebral functioning. Subjects consumed decaffeinated coffee either with or without added caffeine at 2 mg/kg body weight. They were then required to identify letter-pairs as the same or different. Same was defined as two identical letters irrespective of case (AA, Aa); different was defined as two different letters irrespective of case (AB, Ab). Main effects of stimulus type were found for both accuracy and speed of response. In the noncaffeine condition pattern-matching was faster by the right hemisphere and phonologic matching was faster by the left hemisphere. These results replicate much previous work, but under caffeine, a previously unreported reversal in the balance of hemispheric processing efficiency was found. An explanation is offered in terms of the disruption of the normal, optimum, rate of cerebral processing for each hemisphere.

Implicit memory for stimuli presented during inhalation anesthesia in children

During general inhalation anesthesia, neutral phrases including either the color blue or yellow combined with one of two objects, ball or kite, were repeatedly presented to 36 children undergoing eye surgery. Postoperative testing with a coloring and two-choice task was performed to detect preferences for the colors and objects presented under anesthesia. No preference attributable to implicit memory could be demonstrated, and there was no explicit recollection of intraoperative events. Memory of intraoperative events occurring during inhalation anesthesia was not demonstrated with the present methodology in young children.

Effects of post-trial administration of nicotine on human memory: evaluating the conditions for improving memory

In the studies reported here, we investigated the effects of nicotine on memory for unrelated word lists. Nicotine was delivered through cigarette smoking, and memory performance was assessed using both intentional and incidental recall tasks, and employing an additional, indirect measure of memory. We report the results of four experiments in which we manipulated 1) the intake of nicotine using nicotine-containing and nicotine-free cigarettes, 2) the associative aspects of the word-sets, by unrelated words and category words and by instructing subjects to use an associative mnemonic strategy, 3) the opportunity for rehearsal between the presentation and recall, and 4) the time of nicotine administration, post- or pre-trial. We found a positive effect of post-trial nicotine on memory in the incidental recall task, as indicated by enhanced repetition priming, but no effect of nicotine on either immediate recall or pronunciation times (experiments 1 and 2). In experiment 3 we examined the effects of post-trial nicotine using associative and unrelated word-lists, when volunteers were instructed to use an associative mnemonic strategy. We found no main effect of nicotine, but when volunteers were distracted from rehearsal, related words were recalled better than unrelated words. Experiment 4 was a positive control for the timing of nicotine administration within our experimental design, and this showed that pre-trial nicotine not only improved free recall but differentially enhanced the recall of category words over unrelated words.(ABSTRACT TRUNCATED AT 250 WORDS)

[Disorders in cognitive activity and their neuropharmacological correction in structural-functional failure of the head of the caudate nucleus in cats]

The caudate nucleus' head was shown to take part in organisation of praxis, perception, gnosis and "thinking activity". A wide range of dysfunctions in the caudate insufficiency was abolished by a specific set of psychotropic drugs acting upon classic neurotransmitter systems of the cat brain.

Prediction of response to haloperidol dose reduction by Span of Apprehension measures for treatment-refractory schizophrenic patients

Thirteen treatment-refractory schizophrenic patients participated in a haloperidol reduction study. Two of the subjects were unable to tolerate medication reduction. These subjects were comparable to the other patients in terms of initial clinical variables but were outliers on baseline accuracy and reaction time measures from the Span of Apprehension. The results suggest that aspects of basic visual processing and motor response speed may identify patients who require higher neuroleptic doses.

Apomorphine blocks form-deprivation myopia in chickens by a dopamine D2-receptor mechanism acting in retina or pigmented epithelium

Studies of form-deprivation myopia (FDM) in animal models have shown that postnatal ocular growth is regulated by the quality of patterned images on the retina. One of the major challenges in myopia research is to identify the biochemical mechanisms which translate retinal visual responses into signals that regulate scleral growth. Dopamine (DA) has been implicated in this process, since retinal DA levels decline in FDM and subconjunctival injections of apomorphine (Apo, a nonspecific DA agonist) prevent FDM in a dose-dependent way (Stone et al., 1989). To gain insight into where and how DA ligands act to regulate ocular elongation, we compared the action and distribution of DA receptor ligands injected intravitreally vs. subconjunctivally in young chicks. Ocular length was measured by A-scan ultrasound. We found that daily intravitreal injections of Apo block FDM at a 50% effective dose (ED50) of 5 pg per day, or a peak concentration in the vitreous humor of 108 pM, compared to an ED50 of 2.5 ng for subconjunctival injections as reported by Stone et al. (1989, 1990). [3H]-spiperone, a D2-receptor antagonist, reached average maximum retinal concentrations of 160 pM and 260 pM, during the first hour after intravitreal and subconjunctival administration, respectively, at the ED50 dose. In contrast, the maximum spiperone concentrations in the retinal pigment epithelium (RPE) were 30 pM and 410 pM, respectively, after intravitreal or subconjunctival ED50 doses. Spiperone concentrations in sclera after ED50 doses to the two sites differed by 4 x 10(4) (0.4 pM vs. 1.7 nM, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Visual effects of damage to P ganglion cells in macaques

Four indices of visual performance were measured in control macaques and in macaques that had been exposed to monomeric acrylamide, a neurotoxicant that preferentially damages P retinal ganglion cells. Morphological examination of the retina and visual pathways of these monkeys showed virtually complete loss of P ganglion cells over a region extending to at least 40 deg from the fovea, and relative sparing of M ganglion cells. The four tests examined visual functions for which the visual pathway from P ganglion cells might be of great importance: visual acuity, contrast discrimination, hyperacuity, and shape discrimination. In the acrylamide-dosed monkeys, visual acuity was reduced slightly more than fourfold, a somewhat larger reduction than that seen previously after ibotenic-acid lesions of the P pathway in the geniculate. The residual acuity was in good agreement with the Nyquist frequency calculated from the density of ON or OFF M ganglion cells. Contrast increment thresholds were elevated for the dosed monkeys only in one of the two conditions tested. The elevation was found only under those spatiotemporal conditions for which we have previously shown that contrast thresholds are increased by acrylamide exposure, and was most marked at low background contrasts. Vernier acuity was elevated in one dosed monkey, but not affected in a second monkey that also had severe loss of P ganglion cells. Finally, we found no effect of acrylamide exposure on the number of training trials required to learn simple or complex shape discriminations. These results support previous findings in showing that the P pathway mediates visual acuity, and they show that several other important aspects of visual perception are not exclusively dependent on the P pathway.

[The effect of cholinergic substances on the mechanisms of visual recognition in monkeys]

In monkeys (Macaca mulatta) instrumental reflex was elaborated with differentiation of black-and-white and colour visual stimuli in condition of systemic administration of pharmacological preparations selectively influencing the functional state of cholinergic brain structures. Differentiation of black-and-white and colour stimuli is not disturbed by atropine (0.1 mg/kg) and amizile (up to 1.5 mg/kg) injections; at greater doses frustration of the instrumental reflex takes place. Differentiation of black-and-white and colour stimuli is disturbed at injection of various doses of antidepressant phthoracizine: 5 mg/kg and 7 mg/kg, respectively. These disturbances are restored by the injection of definite doses of galantamine; for correction of colour differentiation a greater dose is required. The obtained data point to differences in neurophysiological and neurochemical processes responsible for black-and-white and colour vision.

Medication may be required for the development of automatic information processing in schizophrenia

Medicated and unmedicated schizophrenic patients and normal subjects (n's = 4) were examined on the extent to which their information-processing performance became automated over time, as reflected by increased competence in dual task performance. The central task was a computerized version of the Continuous Performance Test, and the secondary task was a word-list shadowing task. Normal subjects and medicated schizophrenic patients became much more efficient at performing both tasks simultaneously with practice, with unmedicated patients showing no improvement over time.

Pyroglutamic acid improves the age associated memory impairment

Pyroglutamic acid (PCA) was compared with placebo in a randomized, double blind trial for assessing its efficacy in treating memory deficits in 40 aged subjects. Twenty subjects were treated with PCA and 20 with placebo over a period of 60 d. Memory functions were evaluated at baseline and after 60 d of treatment by means of a battery made up of 6 memory tasks. The results suggest that PCA is effective in improving some verbal memory functions in subjects affected by age-related memory decline.

Nimodipine alters acquisition of a visual discrimination task in chicks

Chicks 5 days old received intraperitoneal injections of nimodipine 30 min before training on either a visual discrimination task (0, 0.5, 1.0, or 5.0 mg/kg) or a test of separation-induced distress vocalizations (0, 0.5, or 2.5 mg/kg). Chicks receiving 1.0 mg/kg nimodipine made significantly fewer visual discrimination errors than vehicle controls by trials 41-60, but did not differ from controls 24 h later. Chicks in the 5 mg/kg group made significantly more errors when compared to controls both during acquisition of the task and during retention. Nimodipine did not alter separation-induced distress vocalizations at any of the doses tested, suggesting that nimodipine's effects on learning cannot be attributed to a reduction in separation distress. These data indicate that nimodipine's facilitation of learning in young subjects is dose dependent, but nimodipine failed to enhance retention.

Reduced performance in tests of memory and visual abstraction in seamen exposed to industrial solvents

Eighty-five seamen exposed to a variety of organic solvents and hydrocarbon compounds during their work on chemical tankers were compared with 59 unexposed seamen. Visual memory, auditory memory and visual abstraction were examined 14 days or more after the last solvent exposure. Multivariate analyses were performed to control the effects of confounding factors such as age, alcohol consumption, smoking, cerebral concussions and educational level. Significant correlations were found between increasing solvent exposure and poor results in tests of auditory memory and visual abstraction. These results indicate adverse psychological effects caused by chronic organic solvent exposure.

Effect of alcohol on visual constancy values and possible relation to driving performance

The effects of the constancy phenomena in vision seem to be to provide information about the environment which is not solely dependent upon the characteristics of shape or size of the retinal image but which is modified by the brain to appear closer to the idealized characteristics of the real object. There is a regression away from the retinal image towards the actual object's characteristics. A plate viewed from an angle tends to look more like a disc than would be predicted from the geometry of perspective. This ability of the brain to impose conditions on perception is a high-level process which may be adversely affected by the depressive action of alcohol on the nervous system. In this case, objects such as road signs, etc. would tend to look smaller and so more distant than when sober if regression is inhibited. Drivers' reactions may be delayed if hazards are seen smaller and further away, thereby increasing the possibility of accident. This research indicates a reduction in phenomenal regression after ingestion of alcohol. There are implications for accident-rates in driving or in industry.

Areal influences on complex cells in cat striate cortex: stimulus-specificity of width and length summation

In single neurones recorded from the striate cortex of cats anaesthetized with N2O/O2/halothane, receptive field dimensions, length specificity and areal extent of drive were assessed for different classes of visual stimuli. Receptive fields were mapped as rectangular minimum response fields (MRFs). Spatial summation along the axis of preferred orientation was assessed: for moving bars whose length was varied (length summation); and for height variation of a square-wave grating patch against a uniform grey background, or a patch of moving texture against a stationary background of similar texture. In complementary tests a moving square-wave grating background was progressively occluded by a uniform grey foreground mask of variable height; or a mask of stationary texture of variable height progressively occluded a background of moving texture. In parallel measurements, the width of grating or textured patches or masks was varied whilst maintaining height constant. Broadly speaking, the areal influence of each class of stimulus was comparable, and distinct from extra-receptive field phenomena in evoking responses from within the receptive field, but not from surrounding areas. The masking paradigm provided the most sensitive measure of receptive field height and width. However, in some neurones length summation, the degree of end-stopping, and the directional bias depended critically on the stimulus configuration used. Length summation tended to be more dramatic for short bars than for gratings. Length summation for texture was significantly more pronounced than for an oriented bar in special and in intermediate complex neurones. By contrast, endstopping was typically less intense for gratings than for bars, and least pronounced for texture. Because of stimulus specificity, complex neurones assigned to particular functional subgroups on the basis of their response to oriented bars may exhibit quite different patterns of behaviour for other classes of stimuli.

Cross-modal functions in alcoholism and aging

Two experiments were performed to measure separate aspects of cross-modal functions in normal and alcoholic research participants: matching, and utilization of concepts. In Experiment 1, cross-modal equivalence-matching was measured, i.e. the ability to select in a second modality (e.g. vision), the same stimulus that was first presented in a different modality (e.g. touch). Experiment 2 measured cross-modal transfer of information about stimulus dimensions, i.e. the ability to recognize and use the concepts of texture and form, based upon prior experience solving tactual problems, to solve visual problems. Fifty-five normal and alcoholic research participants comprised the following five groups: 13 young normals (YN) and 10 young alcoholics (YA), 28-48 years of age; 13 older normals (ON) and 14 older alcoholics (OA), 50-71 years of age; and 5 alcoholic Korsakoff patients (K), 55-68 years of age. Separate subgroups of 9 age-matched ONs and 9 OAs were devised for purposes of statistical analyses of data involving the 5 Ks. Results of the experiments indicated that aging is associated with decline in tactual discrimination ability. Further, cross-modal functions appear to be compromised by alcoholic Korsakoff's disease, and--to a lesser extent--by the combined effects of alcoholism and normal chronological aging. Brain mechanisms important for normal cross-modal functions are discussed.

The effect of alcohol intoxication on primary and secondary processes in male social drinkers

The acute effects of alcohol intoxication on cognitive style and on locus of control was investigated in an experimental setting. Sixty male subjects were randomly assigned to either an Alcohol, a Placebo, or a Control group. The alcohol dose was 1.0 ml of 100% alcohol/kg body weight. Subjects filled out a modified version of Rotter's locus of control scale and reported their perceptions to Street's Gestalt Completion Test. The latter test was scored in a standardized way for stimulus closeness, indicating a reality oriented and rational functioning, and stimulus distance, indicating a more primitive, irrational and pleasure oriented functioning. Alcohol made subjects less internally controlled and decreased the reality oriented functioning while the pleasure oriented functioning was not affected. Results were discussed in terms of pharmacological mechanisms, disinhibition, and creativity.