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Trigeminal orosensation and ingestive behavior in the rat.

A deafferentation procedure was used to examine the contributions of trigeminal orosensation to the control of ingestive behavior in the rat. The procedure removed somatosensory input from the mouth, sparing olfaction, lingual taste, and vibrissae inputs as well as proprioceptive afferents from and efferents to the jaw muscles. Rats with sections of tongue or jaw muscle efferents served as oromotor controls. Bilateral trigeminal orosensory deafferentation was followed by an array of effects on ingestive behavior whose magnitudes were proportional to the extent of the deafferentation. The "trigeminal syndrome" includes a disruption of food and water intake (aphagia, adipsia), impairments in the sensorimotor control of eating and drinking, decreased responsiveness to food and water, and a reduction in the level of body weight regulation. Trigeminal deafferentation spared elementary ingestive movement patterns (biting, licking, chewing) but disrupted their control by the perioral stimuli, which normally elicit them, so that eating and drinking sequences were either aborted or inefficient. Deficits in food intake varied with the sensory properties of the diet. Recovery of intake took place along a palatability gradient, and recovery of water intake paralleled that of dry food. The chronically reduced body weight was caused by a persistent hypophagia and reflects reduced responsiveness to food. These findings suggest a considerable degree of overlap in the neural mechanisms mediating the sensorimotor and motivational control of intake in the rat.

Alveolar Process↗

Regional gray matter volumetric changes in autism associated with social and repetitive behavior symptoms.

BACKGROUND: Although differences in brain anatomy in autism have been difficult to replicate using manual tracing methods, automated whole brain analyses have begun to find consistent differences in regions of the brain associated with the social cognitive processes that are often impaired in autism. We attempted to replicate these whole brain studies and to correlate regional volume changes with several autism symptom measures. METHODS: We performed MRI scans on 24 individuals diagnosed with DSM-IV autistic disorder and compared those to scans from 23 healthy comparison subjects matched on age. All participants were male. Whole brain, voxel-wise analyses of regional gray matter volume were conducted using voxel-based morphometry (VBM). RESULTS: Controlling for age and total gray matter volume, the volumes of the medial frontal gyri, left pre-central gyrus, right post-central gyrus, right fusiform gyrus, caudate nuclei and the left hippocampus were larger in the autism group relative to controls. Regions exhibiting smaller volumes in the autism group were observed exclusively in the cerebellum. Significant partial correlations were found between the volumes of the caudate nuclei, multiple frontal and temporal regions, the cerebellum and a measure of repetitive behaviors, controlling for total gray matter volume. Social and communication deficits in autism were also associated with caudate, cerebellar, and precuneus volumes, as well as with frontal and temporal lobe regional volumes. CONCLUSION: Gray matter enlargement was observed in areas that have been functionally identified as important in social-cognitive processes, such as the medial frontal gyri, sensorimotor cortex and middle temporal gyrus. Additionally, we have shown that VBM is sensitive to associations between social and repetitive behaviors and regional brain volumes in autism.

Adolescent↗

Testing the NMDA, long-term potentiation, and cholinergic hypotheses of spatial learning.

The problems and issues associated with the use of pharmacological antagonists in studies on learning and memory are considered in a review of the role of N-methyl-D-aspartate (NMDA) receptors, NMDA receptor-mediated long-term potentiation (LTP), and muscarinic receptors in spatial learning in the water maze. The evidence indicates that neither NMDA nor muscarinic receptors, nor NMDA receptor-mediated LTP, are required for spatial learning, although they might normally contribute to it. Detailed behavioral analyses have indicated that the water maze task is more complex than generally has been appreciated, and has a number of dissociable components. Naive rats trained under NMDA or muscarinic antagonism display sensorimotor disturbances that interfere with their ability to acquire the task. Rats made familiar with the general requirements of the task can learn the location of a hidden platform readily under NMDA or muscarinic antagonism. The ability of a rat to acquire the water maze task depends on its ability to apply instinctive behaviors to performance of the task in an adaptive manner. The instinctive behaviors undergo modification as the rat learns the general strategies required in the task. The evidence suggests that at least some of the plastic changes involved in acquiring the task occur in existing neural circuits situated in widespread areas of the brain, including sensory and motor structures in the cortex and elsewhere, and are therefore difficult to distinguish from existing sensorimotor mechanisms. More generally, the findings indicate the difficulty of inferring the occurrence or nonoccurrence of learning from behavior, and the difficulty of causally linking the action of particular receptor populations with the formation of specific memories.

Animals↗

Effect of myristoylated alanine-rich C kinase substrate (MARCKS) overexpression on hippocampus-dependent learning and hippocampal synaptic plasticity in MARCKS transgenic mice.

The myristoylated alanine-rich C kinase substrate (MARCKS) is a primary substrate of protein kinase C (PKC) thought to regulate membrane-filamentous actin cytoskeletal plasticity in response to PKC activity in the regulation of synaptic efficacy. We have recently reported that MARCKS expression is significantly elevated (45%) in the hippocampus of DBA/2J mice, which exhibit impaired hippocampus-dependent learning and hippocampal long-term potentiation (LTP), compared with C57BL/6J mice. The latter finding led us to hypothesize that elevations in MARCKS expression are detrimental to hippocampal plasticity and function. To assess this more directly, we examined hippocampal (CA1) paired-pulse facilitation and LTP, and hippocampus-dependent learning in mice overexpressing MARCKS through the expression of a human MARCKS transgene (Tg+). The human MARCKS protein was confirmed to be expressed in the hippocampus of Tg+ mice but not in Tg- mice. Schaffer collateral paired-pulse facilitation, input-output responses, and LTP did not differ between Tg+ and Tg- mice, indicating that neurotransmitter release, short-term, and long-term synaptic plasticity are not impaired by MARCKS overexpression. In the Morris water maze, Tg+ mice exhibited a mild but significant spatial learning impairment during initial acquisition, and a more severe impairment during reversal training. Tg+ did not exhibit impaired swim speed or visible platform performance relative to Tg- mice, indicating the absence of gross sensorimotor deficits. Fear conditioning to either context or cue was not impaired in Tg+ mice. Behavioral deficits could not be attributed to differences in hippocampal PKC isozyme (alpha beta(II), gamma, epsilon, zeta) or calmodulin expression, or alterations in hippocampal cytoarchitecture or infrapyramidal mossy fiber limb length. Collectively, these results indicate that elevations in MARCKS expression are detrimental to specific aspects of hippocampal function.

Animals↗

Limb apraxia: cortical or subcortical.

Ideomotor apraxia is defined as a disturbance in timing, sequencing, and spatial organization of gestural movements. Left hemisphere motor dominance reflected by ideomotor apraxia mainly refers to spatially and temporally complex movements performed outside the natural context. While clinicoanatomical studies have failed to unveil a specific lesion correlating with apraxia, white matter damage-interrupting corticocortical and corticosubcortical connections-seems crucial for the deficit to be persistent and severe. Patients with basal ganglia lesions and disorders, such as Parkinson's disease and progressive supranuclear palsy, may exhibit ideomotor apraxia. The putative roles of the basal ganglia in object-oriented action, and therefore in praxis, would include among others (a) the selection of the kinematic parameters and the direction of arm movements, (b) working as an integral part of brain systems involved in timing and representation of action sequences, (c) encoding behavioral context, and (d) working as a subcortical component of the parietofrontal circuits devoted to sensorimotor transformation (e.g., reaching). Several studies suggest that basal ganglia pathology per se may not cause overt apraxia. However, when it is combined with dysfunction of the cortical components of the neural systems involved in sequencing, sensorimotor transformation, and response selection, different types of ideomotor praxis deficits would become clinically manifested.

Apraxia, Ideomotor↗

Baclofen reverses the reduction in prepulse inhibition of the acoustic startle response induced by dizocilpine, but not by apomorphine.

RATIONALE: Since baclofen, the prototypical GABA(B) receptor agonist, is known to reduce the activity of dopaminergic mesolimbic neurons, a putative antipsychotic property of this compound has been suggested, but the evidence for this is still controversial. OBJECTIVES: The aim of the present study was to elucidate the effects of baclofen on the prepulse inhibition (PPI) of the acoustic startle response (ASR), a behavioral paradigm considered to be one of the most powerful tools for the evaluation of sensorimotor gating and for the screening of antipsychotics. METHODS: We tested the effects of baclofen (1.25, 2.5, 5 and 10 mg/kg IP) in rats, per se and in co-treatment with some of the substances known to induce a robust reduction of PPI, such as apomorphine (0.25 mg/kg SC) and dizocilpine (0.1 mg/kg SC). Finally, in order to ascertain whether the effects of baclofen could be ascribed to its activity on GABA(B) receptors, we analyzed whether its action could be prevented by pretreatment with SCH 50911, a selective GABA(B) receptor antagonist (20 mg/kg IP). All the experiments were carried out using standard procedures for the assessment of PPI of the ASR. RESULTS: Baclofen per se produced no significant change in PPI parameters. Moreover, while no effect on apomorphine-mediated alterations in PPI parameters was observed, baclofen proved able to reverse dizocilpine-induced PPI disruption, and this effect was significantly prevented by SCH 50911. On the other hand, this last compound exhibited no effects per se at the same dose. CONCLUSIONS: These results indicate that GABA(B) receptors are implicated in the neurobiological circuitry accounting for glutamatergic action in sensorimotor gating, and therefore can be proposed as putative new targets in the pharmacological therapy of psychotic disorders. Further studies should be addressed to evaluate more closely the clinical efficacy of baclofen in this respect.

Acoustic Stimulation↗

Attenuation of acoustic and tactile startle responses of vitamin B-6 deficient rats.

Vitamin B-6 deficient rats exhibit changes in behavior, sensory function, and other nervous system abnormalities such as convulsive seizures and motor disturbances. Sensorimotor reactivity was evaluated quantitatively by measuring auditory and tactile startle responses in 12 week old female Long-Evans rats fed a diet devoid of added vitamin B-6 (DEF) or a control diet, either ad lib (AL-CON) or pair-fed to deficient rats (PF-CON). Deficiency was confirmed with a tryptophan-load test administered to a separate group of rats fed simultaneously according to the same protocol. At week 18, body weight and feed efficiency were different among groups (p less than 0.001), and were lowest in DEF. Amplitude of response to both acoustic and tactile stimuli was depressed in DEF compared to both control groups, which generally did not differ in response. This effect was seen most dramatically in responses to the acoustic stimulus (p = 0.034), and especially to the first presentation (p = 0.017). Latency to maximum response was not affected by diet. Possible mechanisms for this nervous system abnormality, not previously reported in vitamin B-6 deficiency, are discussed.

Animals↗

Morphological abnormalities and sensorimotor deficits in larval fish exposed to dissolved saxitoxin.

The dietary uptake of one suite of dinoflagellate-produced neurotoxins, that are commonly called paralytic shellfish poisoning (PSP) toxins, is known to cause acute fish kills. However, little is known about the effects of dissolved phase exposure and the potential sublethal effects of this route of exposure on early developmental stages of fish. Toxin exposure during early development is of particular concern because the embryos and larvae of some marine fish species may be unable to actively avoid the dissolved toxins that algal cells release into the water column during harmful algal blooms. Here we use the zebrafish (Danio rerio) as a model experimental system to explore the sublethal effects of a dissolved PSP toxin, saxitoxin (STX), on early development in fish, including sensorimotor function, morphology, and long-term growth and survival. Aqueous phase exposures of 229 +/- 7 microg STX eq. l(-1) caused reductions in sensorimotor function as early as 48 h postfertilization (hpf) and paralysis in all larvae by 4 days postfertilization (dpf). Rohon-Beard mechanosensory neurons appeared to be more sensitive to STX than dorsal root ganglion neurons at this dose. Additionally, exposure to 481 +/- 40 microg STX eq. l(-1) resulted in severe edema of the eye, pericardium, and yolk sac in all exposed larvae by 6 dpf. The onset of paralysis in STX-exposed larvae was stage-specific, with older larvae becoming paralyzed more quickly than younger larvae (5 h at 6 dpf as compared to 8 and 46 h for 4 and 2 dpf larvae, respectively). When transferred to clean water, many larvae recovered from the morphological and sensorimotor effects of STX. Thus, the sublethal effects of the toxin on larval morphology and behavior were reversible. However, zebrafish exposed to STX transiently during larval development (from 2 to 4 dpf) had significantly reduced growth and survival at 18 and 30 days of age. Collectively, these data show that (1) dissolved phase STX is bioavailable to fish embryos and larvae, (2) the toxin is a paralytic with potencies that are stage-specific for fish larvae, (3) the observed toxicological effects of STX exposure are reversible, and (4) a short-term toxin exposure can negatively impact the survival of fish several weeks later. Dissolved algal toxins may therefore have important sublethal effects on vulnerable species of fish.

Animals↗

Prepulse inhibition is different in two inbred mouse strains (CPB-K and BALB/cJ) with different hippocampal NMDA receptor densities.

OBJECTIVE: The hypo-glutamatergic hypothesis of schizophrenia is not only based on the phencyclidine-(PCP)-induced psychosis in mentally healthy humans but also on studies with schizophrenic patients showing deficits in post mortem hippocampal N-methyl-d-aspartate (NMDA) receptor gene expression and deficits in prepulse inhibition. The inbred mouse strains CPB-K and BALB/cJ display considerable differences in hippocampal NMDA receptor densities. Therefore, our working hypothesis was based on the assumption that the CPB-K mouse strain, which has a lower NMDA receptor density in hippocampal CA1, might be a possible animal model for schizophrenia. For this purpose, the inbred mouse strains CPB-K and BALB/cJ were compared by using a sensorimotor gating paradigm. METHODS: Acoustic startle response (ASR) and prepulse inhibition (PPI) of the startle reflex were measured. RESULTS: CPB-K mice displayed a significantly higher ASR and a significantly lower magnitude of PPI as compared to BALB/cJ mice. The test-retest reliability was approved for PPI in both mouse strains, which was performed in repeated sessions over 13 weeks. In summary, our working hypothesis was confirmed that lower levels of hippocampal NMDA receptor densities correspond to lower sensorimotor gating in CPB-K mice. Based on this finding, further experiments using different behavioral paradigms have to be carried out to establish the CPB-K mouse strain as an animal model of schizophrenia.

Acoustic Stimulation↗

Mu rhythm modulation during changes of visual percepts.

Cooperation between vision and somatomotor behavior, such as manual exploration of objects, suggests close functional coupling between the visual and sensorimotor systems. We observed this type of interaction in human volunteers during binocular rivalry while following the level of sensorimotor mu rhythm with a whole-scalp neuromagnetometer. The observers viewed a weak vertical grating in the lower visual field of one eye and a strong horizontal grating in the same spatial window of the other eye. When stationary, the weak grating was permanently invisible because of its low contrast and spatial frequency. A sudden brief drifting movement of the weak grating wiped out the dominant grating, and the weak grating became visible for less than the 3-s interval between the movements. The postcentral 8- to 15-Hz mu rhythm was found in six of nine observers, and its level increased transiently by 10-15%, starting about 450 ms after the beginning of the movement. The mu level was also enhanced by the actual disappearance of the stronger stimulus, when it occurred in random order with the rivalry stimuli. Identical visual motion, when not accompanied by a perceptual dominance change, produced only minor effects on the mu rhythm. Our results show that a change in visual percept, even with no real or imagined motor response, is associated with modified activity of the postcentral gyrus. This modification may reflect visuohaptic interactions and/or activity of the distributed cortical network implementing visually guided movements.

Adult↗

Changes in NADPH-diaphorase positivity induced by status epilepticus in allocortical structures of the immature rat brain.

The distribution and time course of changes of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) positivity were studied in immature rats (12 and 25 days old) surviving motor status epilepticus (SE) induced by a high dose of pilocarpine. Motor SE characterized by continuous convulsions was interrupted after 2 h by an injection of clonazepam (0.5 mg/kg or 1 mg/kg in 12- and 25-day-old rats, respectively) in order to reduce mortality. Correlation between electroencephalographic and behavioral seizure activity was confirmed using animals with electrodes implanted bilaterally in the hippocampus and sensorimotor cortex. Brains were examined 2, 6, 13, and 21 days after motor SE using NADPH-diaphorase histochemistry. Two types of changes were found in both age groups: (a) decrease of NADPH-d positivity occurred in both neuropil and cell bodies in piriform, periamygdalar, and entorhinal cortices; and (b) NADPH-d positivity was induced in the cell bodies in the hippocampal fields CA1/2, CA3, and dentate gyrus. These changes were more intense in animals surviving SE at postnatal day 25 than in younger age group, and they peaked 2 days after SE. The changes observed after SE disappeared quickly in 12-day-old rat pups, where only moderate changes could be observed in piriform, periamygdalar, and entorhinal cortices 6 days after SE, whereas the changes in the histochemical positivity persisted in older animals even 21 days after SE.

Aging↗

MRI-based morphometric topographic parcellation of human neocortex in trichotillomania.

The purpose of the present study was to test specific hypotheses regarding volumetric changes of the neocortex between 10 female trichotillomania (TTM) subjects and 10 female normal controls. A standard three-dimensional (3-D) brain coordinate system was imposed over each newly acquired native magnetic resonance imaging (MRI) scan for positional normalization and 3-D shape/geometric localization analyses were based on the midpoints of anterior and posterior commissures, and the longitudinal fissure. The brain segmentation method, using well-characterized semiautomated intensity and differential contour algorithms by signal intensity-frequency histograms, was used blind to segment the principal gray and white matter structures. The segmented neocortical ribbon was subdivided into 48 regions (i.e. parcellation units) per hemisphere via a new method of morphometric topographic parcellation. There were no significant volumetric changes of the precentral gyrus, postcentral gyrus, supplementary motor cortex or opercular cortex in TTM patients compared with control subjects. A broader analysis as a hypothesis-generating post-hoc effort showed that TTM subjects exhibited significantly reduced left inferior frontal gyrus volume of 27% (t = 2.21, d.f. = 18, P = 0.04) and enlarged right cuneal cortex volume of 40% (t = -2.30, d.f. = 18, P = 0.03) compared to normal controls. This is the first report of a structural neocortex abnormality in TTM. Results are discussed in terms of the behavioral specialization of these two brain neocortical regions and the complex interractions between visual and sensorimotor cortices. The results also showed the feasibility of the MRI-based morphometric topographic parcellation for investigation of the human neocortex in neuroscience research.

Adult↗

Sensorimotor mapping and oropharyngeal reflexes in goldfish, Carassius auratus.

The vagal lobe of goldfish and some carps is a laminated, specialized lobe of the midmedulla containing both primary sensory terminals and primary motor neurons. Both the sensory and motor components are represented in the lobe in a matching, orotopic fashion, i.e. the oral cavity is mapped across the surface of the lobe. Anatomical tracing studies reveal that the circuitry exists for a point-to-point reflex system in which the superficial sensory layers are mapped directly onto the underlying motor layer. The utility of this relatively direct sensorimotor coupling appears to be in terms of sorting food within the mouth according to its gustatory properties. The direct coupling between the mapped sensory layer and the similarly mapped motor layer may be a useful model in which to study the evolutionary development of less tightly coupled sensorimotor systems.

Animals↗

Human analog tests of the sixth stage of object permanence.

Two adult cats were tested on multiple invisible displacement. A dowel was established as a secondary reinforcer and hidden in a manner similar to that used to assess the culmination of sensorimotor intelligence in human infants. Three other cats were tested on single invisible displacement, a simpler version of the task. For human infants, this task is used to assess the beginning of mental representation in the sixth and last stage of sensorimotor intelligence. The cats' searches on these tasks were consistent with representation of an unsensed object and fully developed sensorimotor intelligence.

Animals↗

Cervical spinal cord delivery of a rabies G protein pseudotyped lentiviral vector in the SOD-1 transgenic mouse. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004.

OBJECT: Lentiviral vectors may constitute a vehicle for long-term therapeutic gene expression in the spinal cord. In amyotrophic lateral sclerosis, spinal cord sclerosis and altered axonal transport pose barriers to therapeutic gene distribution. In the present study the authors characterize gene expression distribution and the behavioral impact of the rabies G (RabG) protein pseudotyped lentiviral vector EIAV.LacZ through cervical spinal cord injection in control and Cu/Zn superoxide dismutase-1 (SOD-1) transgenic mice. METHODS: Seven-week-old SOD-1 transgenic mice and their wild-type littermates underwent exposure of the cervicomedullary junction and microinjection of RabG.EIAV.LacZ or vehicle. The Basso-Beattie-Bresnahan locomotor score, grip strength meter, and Rotarod assays were used to assess the effects of disease progression, spinal cord microinjection, and lentiviral gene expression. Spinal cords were removed when the mice were in the terminal stage of the disease. The distribution of LacZ gene expression was histologically evaluated and quantified. Direct cervical spinal cord microinjection of RabG.EIAV.LacZ results in extensive central nervous system uptake in SOD-1 transgenic mice; these findings were statistically similar to those in wild-type mice (p > 0.05). Gene expression lasts for the duration of the animal's survival (132 days). The SOD-1 mutation does not prevent retrograde axonal transport of the vector. Three behavioral assays were used to demonstrate that long-term gene expression does not alter sensorimotor function. In comparison with normative data, vector injection and transgene expression do not accelerate disease progression. CONCLUSIONS: Direct spinal cord injection of RabG.EIAV vectors represents a feasible method for delivering therapeutic genes to upper cervical spinal cord and brainstem motor neurons. Distribution is not affected by the SOD-1 mutation or disease phenotype.

Amyotrophic Lateral Sclerosis↗

Paradoxical locomotor behavior of dopamine D1 receptor transgenic mice.

The behavioral effects of augmenting dopamine D1 receptor expression in the brain were investigated in mice incorporating additional copies of the mouse D1 receptor gene. Two transgenic lines showed increases in brain D1 receptor binding sites, which were greatest in extrastriatal regions. The full D1 agonist SKF 81297, when administered systemically to control animals, stimulated a dose-dependent increase in locomotor activity. In contrast, in D1 receptor overexpressing transgenic mice, this drug caused a marked suppression of locomotion due to a decrease in the frequency of movement initiation. Amphetamine and cocaine induced comparable locomotor activation in both transgenic animals and their control littermates. In the transgenic animals, D1 agonist-induced rearing and climbing behaviors were suppressed. However, on rotarod testing, the agonist-treated transgenic and control mice performed comparably, indicating that sensorimotor coordination was unaffected. These studies demonstrate that altering the levels of D1 receptor expression reverses the effects of D1 agonism on locomotor initiation and rearing.

Animals↗

The functional neuroanatomy of Tourette's syndrome: an FDG-PET Study. II: Relationships between regional cerebral metabolism and associated behavioral and cognitive features of the illness.

We analyzed F-18 fluoro-deoxyglucose PET scans carried out in 18 drug-free patients with Tourette's syndrome (TS) in order to evaluate relationships between cerebral metabolism and complex cognitive and behavioural features commonly associated with this disorder. These features (obsessions and compulsions, impulsivity, coprolalia, self-injurious behavior, echophenomena, depression, and measures of attentional and visuospatial dysfunction) were associated with significant increases in metabolic activity in the orbitofrontal cortices. Similar increases, although less robust, were observed in the putamen and, in the case of attentional and visuospatial measures, in the inferior portions of the insula. On the other hand, behavioral and cognitive features were not associated with metabolic rates in other subcortical (midbrain, ventral striatum), paralimbic (parahippocampal gyrus), or sensorimotor regions (supplementary motor area, lateral premotor or Rolandic cortices), in which metabolism had, in some cases more robustly, distinguished these TS patients from controls (Braun et al., 1993). These results suggest that a subset of regions in which metabolic activity appears to be associated with the diagnosis of TS per se, may be explicitly associated with the emergence of complex behavioral and cognitive features of the illness. This is most conspicuous in the orbitofrontal cortices, and it is consistent with the observation that these features resemble the elements of a behavioral syndrome typically seen in patients with lesions of the orbitofrontal cortex.

Adult↗

The changing roles and targets for animal models of schizophrenia.

Unlike disorders of other fields of medicine (eg., diabetes, heart disease), schizophrenia has been only marginally impacted by the study of animal models. This gap reflects the incomplete understanding of the causes and mechanisms of schizophrenia and the resulting lack of defined targets for model development. However, prior attempts at modeling in animals the complex symptoms of schizophrenia have given way to more promising component models. This review will address the evolving field of animal models of schizophrenia with a focus on models of errors in neurotransmission, and of psychophysiological deficits, with a concluding discussion of the present and future promise of genetic-based models. Evolving models based on the long-held conceptualization of schizophrenia as being based on errors in neurotransmission are discussed as regards the integration of newer findings implicating alterations in dopamine, glutamate and neurotensin function in the pathophysiology and pharmacotherapy of schizophrenia. The case for the more recent conceptualization of schizophrenia as a core deficit in information processing and stimulus filtering is discussed. Animal behavioral paradigms that model psychophysiologic constructs of stimulus processing deficits related to schizophrenia include prepulse inhibition (PPI), a model of sensorimotor gating, or latent inhibition (LI), a model of salience learning. These models represent both better supported associations with schizophrenia and more productive targets and are providing important new information regarding the psychopharmacology of schizophrenia. Genetic models of schizophrenia are based on the demonstrated heritability of the disorder and more recent pharmacogenetic findings for antipsychotic medications. Genetic-based animal models use behavioral or molecular genetic techniques to manipulate behaviors related to schizophrenia by altering the frequencies of related genes. The future development of increasingly informative animal models of schizophrenia will be dependent on a more complete understanding of schizophrenia, an integration of findings across animal models and refinements in the criteria used to assess model "validity" that better reflect the changing nature and roles of animal models of schizophrenia.

Animals↗