Giotto's applications of embodied perception: Lateral and vertical dimensions of space.

Giotto's Arena Chapel frescoes, dating from the early fourteenth century, provide salient illustrations of two types of embodied perceptions. One is universal, a consequence of biology and the physical laws of nature, linked to the vertical dimension of space, and impacting on affect and moral judgement. The other is culturally determined, acquired from the direction of reading script and affecting perceptions of directions of movement, time and causality. Giotto's intuitive use of embodiments, the result of a newly evolving realism in painting, may have prompted late mediaeval chapel-visitors to empathize with the storied biblical characters, so that figures that were once only the object of religious veneration and awe were now made into living beings with a shared humanity, resulting in an awakening of a personal agency that fueled the Renaissance and Modernism.

Latent inhibition in ADHD adults on and off medication: a preliminary study.

OBJECTIVE: To determine the effects of stimulant medication on performance of ADHD adults on a selective attention task that assesses the processing of irrelevant stimuli. METHOD: ADHD patients and matched controls were given two sessions of a two-stage visual search-latent inhibition (LI) task. In stage-1, they detected the location of a unique shape presented with homogeneous distractors. In stage- 2, target detection response time was examined as a function of the stage-1 experience with the target or distractor, or both, providing a within-subject measure of LI. In Session-1, the ADHD subjects were off their customary stimulant medication. In Session-2, they were on medication. RESULTS: Off-medicated ADHD subjects exhibited similar LI to that of controls; medicated ADHD subjects exhibited less LI than controls. Group differences in LI were mediated by RTs to the previously task-irrelevant distractor stimulus. CONCLUSION: The attenuated LI of the on-medication ADHD group is attributable to drug action that reduces attentional resources allocated to distractors.

Positive and negative affect produce opposing task-irrelevant stimulus preexposure effects.

In three experiments, groups were exposed to either positive or negative affect video clips, after which they were presented with a series of task-irrelevant stimuli. In the subsequent test task, subjects were required to learn an association between the previously irrelevant stimulus and a consequence, and between a new stimulus and a consequence. Induced positive affect produced a latent inhibition effect (poorer evidence of learning with the previously irrelevant stimulus than with the novel stimulus). In opposition to this, induced negative affect resulted in better evidence of learning with a previously irrelevant stimulus than with a novel stimulus. In general, the opposing effects also were present in participants scoring high on self-report questionnaires of depression (Experiments 2 and 3). These unique findings were predicted and accounted for on the basis of two principles: (a) positive affect broadens the attentional field and negative affect contracts it; and (b) task-irrelevant stimuli are processed in two successive stages, the first encodes stimulus properties, and the second encodes stimulus relationships. The opposing influences of negative and positive mood on the processing of irrelevant stimuli have implications for the role of emotion in general theories of cognition, and possibly for resolving some of the inconsistent findings in research with schizophrenia patients.

Classical eyeblink conditioning and schizophrenia: a short review.

There is considerable evidence for the involvement of cerebellar structures and circuits in classical conditioning of eyeblink responses (EBC) and in the pathophyiology of schizophrenia, leading to the expectation that schizophrenia patients should exhibit impaired EBC. A review of the literature indicates that such a position is not supported. Of the nine published studies, three reported poorer EBS in patients compared to controls, three reported better EBC, and three reported no significant EBC differences between the groups. Overall, medicated schizophrenia patients showed poorer EBC, and non-medicated patients exhibited better or normal EBC, relative to healthy control groups. In the light of those results and the fact that no experiment explicitly compared medicated and non-medicated patients, one cannot assume that the EBC deficits in patient groups are attributable to anything other than an effect from medication.

Obsessive-compulsive disorder patients display enhanced latent inhibition on a visual search task.

Latent inhibition (LI) is a phenomenon that reflects the ability to ignore irrelevant stimuli. LI is attenuated in some schizophrenic patient groups and in high schizotypal normal participants. One study has found enhanced LI in patients with obsessive-compulsive disorder (OCD [Swerdlow, N. R., Hartston, H. J., & Hartman, P. L., 1999. Enhanced visual latent inhibition in obsessive-compulsive disorder. Biological Psychiatry, 45, 482-488]). The present experiment replicated this finding using a within-subject visual search LI task, with OCD patients displaying more LI than healthy controls. The contrasting LI effects in schizophrenia and OCD are discussed in terms of how these groups differentially process relevant and irrelevant stimuli, and how that outcome affects subsequent behavior.

Latent inhibition and asymmetrical visual-spatial attention in children with ADHD.

The research was designed to determine whether the purported hemispheric asymmetries that are associated with attention deficit/hyperactivity disorder (ADHD) affect performance on a selective attention visual search task, and whether any obtained asymmetry will be modulated by methylphenidate. Two groups of children (8-15 years) with ADHD, one with methylphenidate treatment (ADHD+) and one without (ADHD+), were compared to matched controls on a two-stage visual search task. The task assessed right-left visual field asymmetries and the effects of changing a previous distractor into a target. Such a procedure, related to latent inhibition (LI; poorer performance to a previously irrelevant stimulus than to a novel one), can provide evidence for dysfunctional processing of irrelevant stimuli. All three groups exhibited the LI effect. The ADHD group, however, exhibited less LI for left- than right-side targets, an effect absent in the control and ADHD+ groups, suggesting a lateralized attentional deficit for ADHD+ that was normalized by methylphenidate.

The visual search analogue of latent inhibition: implications for theories of irrelevant stimulus processing in normal and schizophrenic groups.

Latent inhibition (LI) is a robust phenomenon that is demonstrated when a previously inconsequential stimulus is less effective in a new learning situation than a novel stimulus. Despite LI's simplicity, there is considerable disagreement as to its theoretical basis. Attentional theories claim that unattended stimulus preexposures reduce stimulus associability. Alternatively, it has been asserted that associability is unaffected and that LI is a result of competition/retrieval processes. The present article reviews a series of visual search studies, some with normal subjects, both undifferentiated and divided into low and high schizotypals, and others with pathologies that entail dysfunctional attention, such as schizophrenia, Parkinson's disease, and anxiety. The visual search conditions were designed to model those of traditional LI experiments, while tapping attentional processes independently of the learning scores that index LI. A variety of evidence from these and other studies is used to support the involvement of attentional and retrieval processes in LI. A model of the mechanism of action of these processes in LI is presented, together with its application to schizophrenia.

Construct validity of the animal latent inhibition model of selective attention deficits in schizophrenia.

Latent inhibition (LI) is demonstrated when a previously unattended/inconsequential stimulus is less effective in a new learning situation than a novel stimulus. In rats and humans, LI is reduced by dopamine agonists and increased by dopamine antagonists. In addition, LI is attenuated in actively psychotic schizophrenia patients, thus conferring strong predictive validity to the animal LI preparation for schizophrenia. However, the validity of the attentional construct in the LI model of schizophrenia dysfunction depends on confirming two assumptions: that animal and human LI share a common process, and that the process is related to selective attention. Evidence to support both assumptions is presented, followed by a description of a conditioned attention theory that emphasizes the role of initial levels of attention elicited by repeated relevant and irrelevant stimuli, and the differences between these levels in schizophrenia and normal groups.

Delay-induced super-latent inhibition as a function of order of exposure to two flavours prior to compound conditioning.

A number of recent conditioned taste aversion (CTA) experiments have demonstrated a super-latent inhibition (LI) effect--namely, a time-induced increase in the effects of stimulus preexposure when the interval between acquisition and test is spent in a context that is different from the other experimental contexts. Two CTA experiments with rats were conducted to examine the role of primacy in producing super-LI. In Experiment 1, one of two flavours was pre-exposed, following which a second flavour was preexposed. After the second preexposure, animals were conditioned by pairing a compound of the two preexposed flavours with LiCl. The test stage was conducted 1 or 21 days after conditioning, with the interval being spent in either the same or different contexts. In the test, animals were confronted with two bottles, each with one of the two preexposed flavours. Super-LI was obtained only for the first preexposed flavour in the 21-day delay group that spent the interval in a different context. Experiment 2 was designed to ensure that the effects in Experiment 1 represented LI, and to control for order of presentation of the flavours and time between preexposure and acquisition. The results replicated those of Experiment 1. The two experiments support the importance of primacy in the general super-LI experiment where CS-alone preexposure precedes CS-US.

There is a time and a place for everything: bidirectional modulations of latent inhibition by time-induced context differentiation.

Latent inhibition (LI) is defined as poorer evidence of learning with a stimulus that previously was presented without consequence, as compared with a novel or previously attended stimulus. The present article reviews the evidence, mostly from three-stage conditioned taste aversion studies (preexposure, conditioning, and test), that LI can be either attenuated or enhanced depending on the length of the retention interval between conditioning and test and where that interval was spent. Time-induced reduction in LI is observed when the interval context is the same as that of the preexposure, conditioning, and test stages. Super-LI is obtained when a long retention interval is spent in a context that is different from that of the other stages. The differential modulations of LI appear to be the result of the strengthening of primacy effects (i.e., first training disproportionately stronger than subsequent training) by long-interval different contexts, thereby producing super-LI, and the reversal of this effect by long-interval same contexts, thereby producing attenuated LI. The bidirectional effects of time/ context modulations on LI, unaccounted for by current learning theories, are explained, in part, by a time-induced context differentiation process. Implications for theories of LI, learning, and, memory are discussed.

The relation between latent inhibition and symptom-types in young schizophrenics.

Latent inhibition (LI), retarded conditioning to a stimulus that has been previously repeatedly presented without reinforcement, was examined in young schizophrenics and normal controls using a within-subject visual search task. Healthy controls exhibited the usual LI effect. LI was potentiated in schizophrenics who simultaneously exhibited high levels of negative symptoms and low levels of positive symptoms. Schizophrenic groups with other combinations of positive and negative symptoms did not differ from controls. The pattern of data suggests that past inconsistencies in the LI-schizophrenia literature may be the result of opposing processes that are associated with positive and negative symptoms.

Effects of post-treatment retention interval and context on neophobia and conditioned taste aversion.

We have repeatedly observed that a delay between acquisition and test, and the nature of the context in which the delay is spent, modulates latent inhibition (LI) of conditioned taste aversion (CTA; e.g. [Anim. Learn. Behav. 28 (2000) 389; Anim. Learn. Behav. 30 (2002) 112]). The present paper analysed the effects of delayed testing and treatment context after flavor exposure on the recovery of neophobia (Experiment 1) and on extinction after simple conditioning (Experiment 2). Two experiments were conducted with the same factorial design (2x2: 1 day versus 21 days of delay between first and second stage, and home versus experimental cages as place of experimental treatment). There were independent effects of both variables on habituation of neophobia and conditioning strength as measured on extinction trials. The long delay produced a reduction of neophobia (Experiment 1) and an increase in conditioning (Experiment 2). In addition, more of the flavored solution was consumed when the experimental treatment was conducted in the home cage than in the experimental cage (Experiment 1), and there was stronger conditioning when the delay period took place in the experimental cages than in the home cages (Experiment 2). The implications of these results for LI, as well as their relevance for experiments that use the CTA paradigm, are discussed.

An empirical analysis of the super-latent inhibition effect.

In three conditioned taste aversion experiments, we examined the roles of several variables in producing super-latent inhibition (LI). This effect, greater LI after a long interval than after a short interval between the conditioning and the test stages (De la Casa & Lubow, 2000), was shown to increase with the number of stimulus preexposures (0, 2, or 4; Experiment 1) and with the length of the delay interval (1, 7, 14, or 21 days; Experiment 2). Furthermore, super-LI was obtained when the delay interval was introduced between the conditioning and the test stages (Experiments 1 and 2), but not when it was introduced between the preexposure and the conditioning stages (Experiment 3). The results are discussed in relation to interference explanations of LI.

Latent inhibition as a function of schizotypality and gender: implications for schizophrenia.

In three within-subject experiments, we demonstrated that preexposure to an irrelevant stimulus interfered with performance when that stimulus subsequently predicted the correct location of a target stimulus. This latent inhibition-like effect (LI) was manifest in response time measures, but not errors. As with other related paradigms, LI was a function of an interaction between schizotypy-level and gender. Low schizotypal females and high schizotypal males exhibited significant LI, while high schizotypal females and low schizotypal males failed to produce LI effects. The results, similar to findings with schizophrenic patients, suggest a sexual dimorphism of cognitive dysfunction in schizophrenia, particularly in regard to the processing of irrelevant stimuli.

Superlatent inhibition and spontaneous recovery: differential effects of pre- and postconditioning CS-alone presentations after long delays in different contexts.

In two pairs of three-stage conditioned taste aversion experiments, we examined the effects of delay interval (1 or 21 days) between the second and third stages, and of context in which the animals spent the delay (same as or different from the context of the other stages) on latent inhibition (LI) and spontaneous recovery following extinction. In the LI experiments (Experiments 1A and 1B), the first stage comprised nonreinforced presentations to saccharin or to water. In the second stage, rats were conditioned by saccharin paired with LiCl. In the extinction experiments (Experiments 2A and 2B), the order of the stages was reversed. For all experiments, Stage 3, the test stage, consisted of three presentations of saccharin alone. There was a super-LI effect in the saccharin-preexposed group that spent the 21-day delay in the different context (Experiment 1A). When the delay was spent in the same context, there was no difference in the amount of LI between the short- and long-delay groups (Experiment 1B). Conversely, there was a spontaneous recovery effect in the long-delay/same-context group (Experiment 2B), but not in the long-delay/different-context group (Experiment 2A). The pattern of results, incompatible with current explanations of delay-induced changes in memory performance, was interpreted in terms of an interaction between the delay conditions (same or different delay context), which modulate the extinction of previously acquired context-CS-nothing associations (during CS-alone presentations), and primacy effects.

Latent inhibition deficits in high-schizotypal normals: symptom-specific or anxiety-related?

Latent inhibition (LI) is the phenomenon in which subjects who have repeatedly experienced an irrelevant stimulus perform more poorly on a new learning task with that stimulus than with a novel stimulus, presumably because of a decline in stimulus-specific attention. The present article reviews the literature on LI deficits in high-schizotypal normal subjects and schizophrenic patients. Although LI-deficits have been thought to be specific to these groups, evidence is presented that the effects may be related to the anxiety components of high-schizotypality and related pathologies.

Performance on the visual search analog of latent inhibition is modulated by an interaction between schizotypy and gender.

Two experiments examined the visual search analog of latent inhibition (LI) and the novel popout (NPO) effect in healthy humans. In Experiments 1 (n=48) and 2 (n=180), subjects judged the positions (left or right side of a computer screen) of a unique target amongst a field of homogeneous distractors. In both experiments, there was a strong LI effect, as indicated by longer response times (RT) to those displays in which the target was previously a distractor and the distractors were previously the target, as compared with displays in which the target was novel and the distractors were previously the target. NPO, faster RT to a display in which the target was novel on a background of familiar distractors than to a display in which both target and distractors were novel, was not obtained. In Experiment 1, LI magnitude was not affected by gender. In Experiment 2, LI magnitude was larger for low schizotypal females than for high schizotypal females, a result not obtained for males. This pattern is similar to one reported for medicated schizophrenic out-patients (Lubow, R.E., Kaplan, O., Abramovich, P., Rudnick, R., Laor, N., 2000. Visual search in schizophrenics: latent inhibition and novel popout effects. Schizophr. Res., in press). Together, these data suggest that the LI deficits found in high schizotypal healthy subjects and in schizophrenic patients represent a dysfunction that is characterized by an inability to reduce attention allocated to irrelevant stimuli, and that this may serve as a trait marker for some subtypes of schizophrenia, particularly those associated with female gender.

Latent inhibition with a response time measure from a within-subject design: effects of number of preexposures, masking task, context change, and delay.

Latent inhibition (LI), poorer performance on a learning task to a previously irrelevant stimulus than to a novel stimulus, was produced in 4 experiments, using a within-subject design and a response time (RT) measure. LI was reduced by decreasing the number of stimulus preexposures, omitting the masking task, changing the context from the preexposure to the test phase, and introducing a delay between the 2 phases. Together, these effects indicate that the within-subject RT-based LI reflects the same processes as those that govern between-subject LI with correct response as the dependent measure. The new procedure provides an advantageous method for assessing attentional dysfunction related to the processing of irrelevant stimuli, particularly in pathological groups, such as patients with schizophrenia.

Stress affects the selection of relevant from irrelevant stimuli.

Two experiments were used to examine the effects of stress on latent inhibition (LI; poorer learning with a previously exposed irrelevant stimulus rather than a novel stimulus). In Experiment 1, stress was induced in college students by threatening participants' self-esteem with a difficult number series completion test that was related to intelligence. In Experiment 2, the participants were job seekers who were either informed or not that the LI test was part of the selection process. In both experiments, LI was attenuated in high- as compared with low-stressed participants. The results suggest that stress and/or anxiety impairs the inhibition of irrelevant-preexposed stimuli. Implications for understanding the impaired selective attentional processes in schizophrenia and schizotypy are discussed.

Visual search in schizophrenia: latent inhibition and novel pop-out effects.

A visual search task was used to assess attentional function in a mixed group of schizophrenic patients and in normal controls. Subjects identified presence or absence of a unique shape presented with homogeneous distractors. Response time (RT) was examined as a function of prior experience with target, distractor, or both. On each trial, targets and/or distractors were either novel or familiar. Schizophrenic patients were slower than controls in all conditions. In the test phase, three target/distractor conditions were examined (PE - target and distractors pre-exposed but reversed; NPE - target novel and distractors pre-exposed; NOV - novel target and distractors). As predicted, normal controls, but not schizophrenics, showed latent inhibition (LI: PE minus NPE). The latter finding was due to the absence of normal LI in female patients. A novel pop-out effect (NOV minus NPE) was obtained which did not interact with any of the other variables. The results suggest that the LI effect is indeed related to the processing of irrelevant stimuli, and that, at least female schizophrenic patients process such stimuli differently from controls. Past inconsistencies in the LI-schizophrenia literature may be the result of disproportionate gender compositions in patient and control groups.