Visual Memory Research Articles

Correlative comparison of visual working memory paradigms and associated models

When studying the working memory (WM), the ‘slot model’ and the ‘resource model’ are two main theories used to describe how information retention occurs. The slot model shows that WM capacity consists of a certain number of predefined slots available for information storage. This theory explains that there is a binary condition during information recall in which information is either wholly maintained within a slot or forgotten. The resource model has a resolution-based approach, suggesting a continuous resource able to be distributed among a number of items in WM capacity. Recently hybrid models have been introduced, suggesting that WM may not strictly conform to only one model. Accordingly, to understand the relationship between two of the most widely used paradigms in WM evaluation, we implemented a correlational assessment in two different psychophysics tasks, an analog recall paradigm with sequential bar presentation and a delayed match-to-sample (DMS) task with checkerboard stimuli. Our study revealed significant correlations between WM performance in the DMS task and recall error, precision, and sources of errors in the sequential paradigm. Overall, the findings emphasize the importance of considering both tasks in understanding WM processes, as they shed light on the debate between the slot and resource models by revealing overlapping elements in both theories and the tasks used to evaluate WM capacity.

Visual feedback and motor memory contributions to sustained motor control deficits in autism spectrum disorder across childhood and into adulthood.

Autistic individuals show deficits in sustained fine motor control which are associated with an over-reliance on visual feedback. Motor memory deficits also have been reported during sustained fine motor control in autism spectrum disorders (ASD). The development of motor memory and visuomotor feedback processes contributing to sustained motor control issues in ASD are not known. The present study aimed to characterize age-related changes in visual feedback and motor memory processes contributing to sustained fine motor control issues in ASD. Fifty-four autistic participants and 31 neurotypical (NT) controls ages 10-25 years completed visually guided and memory guided sustained precision gripping tests by pressing on force sensors with their dominant hand index finger and thumb. For visually guided trials, participants viewed a stationary target bar and a force bar that moved upwards with increased force for 15s. During memory guided trials, the force bar was visible for 3s, after which participants attempted to maintain their force output without visual feedback for another 12s. To assess visual feedback processing, force accuracy, variability (standard deviation), and regularity (sample entropy) were examined. To assess motor memory, force decay latency, slope, and magnitude were examined during epochs without visual feedback. Relative to NT controls, autistic individuals showed a greater magnitude and steeper slope of force decay during memory guided trials. Across conditions, the ASD group showed reduced force accuracy (β = .41, R2 = 0.043, t79.3=2.36, p = 0.021) and greater force variability (β=-2.16, R2 = .143, t77.1=-4.04, p = 0.0001) and regularity (β=-.52, R2 = .021, t77.4=-2.21, p = 0.030) relative to controls at younger ages, but these differences normalized by adolescence (age × group interactions). Lower force accuracy and greater force variability during visually guided trials and steeper decay slope during memory guided trials were associated with overall autism severity. Our findings that autistic individuals show a greater rate and magnitude of force decay than NT individuals following the removal of visual feedback indicate that motor memory deficits contribute to fine motor control issues in ASD. Findings that sensorimotor differences in ASD were specific to younger ages suggest delayed development across multiple motor control processes.

Ultralow Energy Consumption and Fast Neuromorphic Computing Based on La0.1Bi0.9FeO3 Ferroelectric Tunnel Junctions.

Low-power and fast artificial neural network devices represent the direction in developing analogue neural networks. Here, an ultralow power consumption (0.8 fJ) and rapid (100 ns) La0.1Bi0.9FeO3/La0.7Sr0.3MnO3 ferroelectric tunnel junction artificial synapse has been developed to emulate the biological neural networks. The visual memory and forgetting functionalities have been emulated based on long-term potentiation and depression with good linearity. Moreover, with a single device, logical operations of "AND" and "OR" are implemented, and an artificial neural network was constructed with a recognition accuracy of 96%. Especially for noisy data sets, the recognition speed is faster after preprocessing by the device in the present work. This sets the stage for highly reliable and repeatable unsupervised learning.

Visual event boundaries trigger forgetting despite active maintenance in visual working memory.

The contents of visual perception are inherently dynamic-just as we experience objects in space, so too events in time. The boundaries between these events have downstream consequences. For example, memory for incidentally encountered items is impaired when walking through a doorway, perhaps because event boundaries serve as cues to clear obsolete information from previous events. Although this kind of "memory flushing" can be adaptive, work on visual working memory (VWM) has focused on the opposite function of active maintenance in the face of distraction. How do these two cognitive operations interact? In this study, observers watched animations in which they walked through three-dimensionally rendered rooms with picture frames on the walls. Within the frames, observers either saw images that they had to remember ("encoding") or recalled images they had seen in the immediately preceding frame ("test"). Half of the time, a doorway was crossed during the delay between encoding and test. Across experiments, there was a consistent memory decrement for the first image encoded in the doorway compared to the no-doorway condition while equating time elapsed, distance traveled, and distractibility of the doorway. This decrement despite top-down VWM efforts highlights the power of event boundaries to structure what and when we forget.

Influence of presentation duration on filtering of irrelevant stimuli in visual working memory

In environments teeming with distractions, the ability to selectively focus on relevant information is crucial for advanced cognitive processing. Existing research using event-related potential (ERP) technology has shown active suppression of irrelevant stimuli during the consolidation phase of visual working memory (VWM). In previous studies, participants have always been given sufficient time to consolidate VWM, while suppressing distracting information. However, it remains unclear whether the suppression of irrelevant distractors requires continuous effort throughout their presence or whether this suppression is only necessary after the consolidation of task-relevant information. To address this question, our study examines whether distractor suppression is necessary in scenarios where consolidation time is limited. This research investigates the effect of varying presentation durations on the filtering of distractors in VWM. We tasked participants with memorizing two color stimuli and ignoring four distractors, presented for either 50 ms or 200 ms. Using ERP technology, we discovered that the distractor-induced distractor positivity (PD) amplitude is larger during longer presentation durations compared to shorter ones. These findings underscore the significant impact of presentation duration on the efficacy of distractor suppression in VWM, as prolonged exposure results in a stronger suppression effect on distractors. This study sheds light on the temporal dynamics of attention and memory, emphasizing the critical role of stimulus timing in cognitive tasks. These findings provide valuable insights into the mechanisms underlying VWM and have significant implications for models of attention and memory.

Long-lasting pure topographical disorientation due to heading disorientation following left retrosplenial infarction: A report of two cases

Topographical disorientation is linked to lesions in the right hemisphere and typically resolves within a few months post-stroke. Persistent topographical disorientation is uncommon and frequently accompanied by impairments in visual memory, complicating the analysis of the underlying mechanisms. Herein, we report two cases of sustained pure topographical disorientation following cerebral hemorrhages in the left retrosplenial region. The patients exhibited disorientation in both familiar and unfamiliar settings, attributable to heading disorientation, a deficit in determining the directional relationship between one’s current position and a target location or external frames. The patients struggled with reconstructing large-scale spatial frameworks and integrating new egocentric and allocentric perspectives upon changes in body orientation. There were no landmark agnosia, egocentric disorientation, or anterograde disorientation. Although mild verbal memory deficits were observed, no other cognitive impairments, including visual memory deficits, were detected. Our findings imply that lesions confined to the left retrosplenial region can induce enduring heading disorientation and suggest a significant role for this area in processing and integrating spatial information necessary for large-scale navigation. Clarifying the features of topographical disorientation will significantly impact the therapeutic approaches, enhancing the quality of life for affected patients by restoring their independence and mobility.

Reconstructing Spatiotemporal Trajectories of Visual Object Memories in the Human Brain.

How the human brain reconstructs, step-by-step, the core elements of past experiences is still unclear. Here, we map the spatiotemporal trajectories along which visual object memories are reconstructed during associative recall. Specifically, we inquire whether retrieval reinstates feature representations in a copy-like but reversed direction with respect to the initial perceptual experience, or alternatively, this reconstruction involves format transformations and regions beyond initial perception. Participants from two cohorts studied new associations between verbs and randomly paired object images, and subsequently recalled the objects when presented with the corresponding verb cue. We first analyze multivariate fMRI patterns to map where in the brain high- and low-level object features can be decoded during perception and retrieval, showing that retrieval is dominated by conceptual features, represented in comparatively late visual and parietal areas. A separately acquired EEG dataset is then used to track the temporal evolution of the reactivated patterns using similarity-based EEG-fMRI fusion. This fusion suggests that memory reconstruction proceeds from anterior frontotemporal to posterior occipital and parietal regions, in line with a conceptual-to-perceptual gradient but only partly following the same trajectories as during perception. Specifically, a linear regression statistically confirms that the sequential activation of ventral visual stream regions is reversed between image perception and retrieval. The fusion analysis also suggests an information relay to frontoparietal areas late during retrieval. Together, the results shed light onto the temporal dynamics of memory recall and the transformations that the information undergoes between the initial experience and its later reconstruction from memory.

Impact of Cognitive and Psychological Functions in Relapsing-Remitting Multiple Sclerosis: A Cross-Sectional Study.

To compare the cognitive functions and trait anxiety in patients diagnosed with relapsing-remitting multiple sclerosis (RRMS) to those of matched healthy controls (HCs). In addition, the study aims to investigate the correlations among cognitive functions, anxiety, depression, and quality of life (QOL) in this clinical population. The sample included RRMS patients ( n = 21) and an equal number of age-, education-, and sex-matched HCs. Participants were assessed on the Indian version of the Wechsler Adult Intelligence Scale-IV, auditory and visual learning and memory, and visual-spatial construction and memory. RRMS patients were also assessed for levels of anxiety, depression, and their QOL. Comparative analyses between RRMS patients and HCs were carried out for neuropsychological assessments. Correlations among cognitive functions, anxiety, depression, and QOL in RRMS patients were examined. RRMS patients showed significant deficits across various cognitive domains, including processing speed and verbal learning, compared to HCs ( P < 0.05). In addition, they reported higher levels of trait anxiety compared to HCs ( P < 0.01), along with moderate state anxiety and mild depression. A significant correlation among anxiety, depression, and QOL was observed in RRMS patients. This study highlights significant cognitive impairments and psychological distress experienced by RRMS individuals, underscoring the critical need for comprehensive care addressing both cognitive impairments and psychological distress to enhance QOL.

Does Stimulus Category Coherence Influence Visual Working Memory? A Rational Analysis.

Visual working memory (VWM) refers to the temporary storage and manipulation of visual information. Although visually different, objects we view and remember can share the same higher-level category information, such as an apple, orange, and banana all being classified as fruit. We study the influence of category information on VWM, focusing on the question of whether stimulus category coherence (i.e., whether all to-be-remembered items belong to the same semantic category) influences VWM performance. This question is addressed in two behavioral experiments using a change-detection paradigm and a rational analysis using an ideal observer based on a Bayesian model. Both experimental participants and the ideal observer often, but not always, performed numerically better on coherent trials (i.e., when all stimuli belonged to the same category). We hypothesize that the influence of category coherence information on VWM may be task-dependent and/or stimulus-dependent. In conditions when category coherence information is highly valuable for task performance, as indicated by the ideal observer, then participants tended to make use of it. However, when the ideal observer suggested this information was not crucial to performance, participants did not. In addition, both participants and the ideal observer showed a bias toward responding "same," and often showed a stronger influence of category coherence on change trials. The consistencies between participant and ideal observer responses suggest participants often behaved as they did because these behaviors are optimal (or approximately so) for maximizing task performance. This may help explain conflicting results reported in the scientificliterature.

Prospective Memory Complaints Are Related to Objective Performance in People With Multiple Sclerosis

ObjectivesTo examine the association between subjective and objective prospective memory (PM) in people with multiple sclerosis (PwMS). DesignSecondary analysis of a cross-sectional cohort study. SettingCommunity-based comprehensive multiple sclerosis center. ParticipantsPwMS (N=112) who completed a battery that included measures of PM, depression, and fatigue. InterventionsNot applicable. Main Outcome MeasuresObjective PM was measured with the performance-based Memory for Intentions Test (MIST), whereas subjective PM was assessed with the self-report Perceived Deficits Questionnaire-Prospective Memory (PDQ-PM). ResultsPwMS had low scores on the PDDS (median=2) and HADS-D (median=5.29), with 26.8% scoring 1 standard deviation or lower (≤15th percentile) on the MIST. Objective PM was significantly associated with subjective PM in a multivariate model (β=−0.18, P=.036), which accounted for demographics, physical disability, retrospective memory, and depressive and fatigue severity. Physical disability, depression, and fatigue were also significant contributors to subjective PM. Time-based PM performance emerged as the specific component that was associated with subjective PM. ConclusionsThese findings suggest that among PwMS with relatively mild impairment and symptomatology, their objective PM performance was associated with their self-assessments, even when considering retrospective memory and factors that influence their cognitive perceptions. The results expand upon the subjective-objective cognition discrepancy literature in multiple sclerosis and highlights how the PDQ-PM could be used as a complementary measure to help identify difficulties with PM.

FC7: Effects of a multidomain cognitive stimulation program in older adults

Objectives: The aim of this study was to ascertain the influence of a six-month multidomain stimulation program on cognitive functioning.Methods: The sample comprised 25 older adults 60 years-old and older (Mage = 66.08 years), of whom 96% were women and 54% had high education. The intervention program had a duration of six months and was implemented in a group format in one-hour sessions on a weekly basis. Lessons on neuroprotective factors, training in practical compensatory strategies to improve daily performance, cognitive training exercises and recreational cognitive stimulation activities were included. In order to analyze participants’ cognitive functioning the following instruments were used: Mini-Mental State Examination, Rey Complex Figure Test, Digit Span Test, Stroop Test, Trail Making Test (Part A and Part B), Verbal Fluency Test, Boston Naming Test (Short Form) and Neuropsi Verbal Memory Subtest. Wilcoxon test was performed to test the impact of the intervention program on participants cognitive functioning.Results: Statistically significant differences were found after the six-month intervention in verbal memory encoding (W= –2.772, p&lt; 0.05), in spontaneous verbal memory retrieval(freerecall) (W= – 3.456, p&lt; 0.001), inverbal recognition memory (W = –3.184, p &lt; 0.001), in spontaneous visual memory retrieval (W = –2.056, p &lt; 0.05), and in naming by visual confrontation (W = –2.521, p &lt; 0.05). In all cases, participants increased their scores after taking part in multicomponent a six-month multidomain stimulationprogramConclusions: One of the biggest concerns among older people is the loss of cognitive abilities that may occur with ageing. Cognitive stimulation programs, if sufficiently comprehensive, can be a good tool to maintain and improve cognitive functions as we age.

Neuropsychological performance in women at risk of postpartum depression and postpartum psychosis.

While neuropsychological deficits are commonly observed in affective and psychotic disorders, this remains unexplored in these disorders when they occur during pregnancy and the postpartum period. A neuropsychological test battery was administered to women defined at risk of postpartum depression (PD, N = 53) because having either a current or past diagnosis of major depressive disorder, women at risk of postpartum psychosis (PP, N = 43) because of a diagnosis of bipolar disorder or schizoaffective disorder and/or a previous episode of PP and women not at risk (NR, N = 48) in the third trimester of pregnancy. Generalized and specific cognitive abilities were compared between groups. Women at risk of PP presented worse executive functions and processing speed compared to NR and worse performance compared to women at risk of PD across all cognitive domains. In addition, women at risk of PP who developed a psychiatric relapse in the first four weeks post-partum showed worse verbal learning and memory, visual memory, executive functions and processing speed in pregnancy compared to NR, whereas women at risk of PP who remained well presented neuropsychological performance that was intermediate between that of the women NR and those at risk of PP who developed symptoms. There were no differences in performance between women at risk of PD and the NR women, even if 31 women at risk of PD presented depressive symptoms at the time of cognitive assessment. Our findings in women at risk of PP align with neuropsychological findings in individuals with, or at risk of psychosis unrelated to pregnancy. In addition, initial evidence that women at risk of PP who develop a psychiatric relapse in the postpartum show a particularly poor neuropsychological performance in pregnancy suggests that this could be considered part of a phenotype for the disease and help guiding future preventive strategies in this clinical population. In women at risk of PD, the presence of depressive symptoms did not influence cognitive performance.

USE OF TECHNOLOGIES OF HIGHER NERVOUS ACTIVITY AND PSYCHO-PHYSIOLOGICAL HUMAN FUNCTIONS STUDYING IN EXTREME CONDITIONS

Applied techniques and some results of studies the higher nervous activity (HNA) of the people, their psychophysiological functions (PFF) by Ukrainian scientists and doctors were described, as well as influences of extreme conditions on HNA. Aim. Results of the influence of extreme mountain conditions at high altitudes (hypoxia, etc.) demonstration and further research of changes in the psychophysiological functions of the brain under these conditions; description of the developed methods of professional selection. Methods. Comparative analysis of a large number of the data from experiments and observations. Physical, mathematical, program modeling. Methods of HNA, brain research: electroencephalography, diagnosis of personal neurodynamic features, etc. Three methods of PFF research: parameters of the neurodynamic level, parameters of the neuropsychological level, and personal specifics. The adapted questionnaire scheme (QS) based on Cattell's 16-factor personality tests was applied. Results. The influence of hypoxia and other factors of mountain conditions on HNA were studied deeply. The results were presented. Also, there were presented results of registered changes of EEG in such extreme conditions. The influence of a number of stress factors in extreme conditions (hypoxia, etc.) has been demonstrated. Some basic methods of HNA researches used in such conditions were described as well as results of investigations of individual typological features of the nervous systems were presented. Methods for human psychophysiological functions studying were described. Studies of human personal characteristics were described in details. Data recorded by the PNN-3 device were taken for the diagnosis of personal neurodynamic features. The parameters of the neuropsychological level were determined using the following methods: "triangles" (the level of development of short-term visual memory), "instrument scales" (working memory, attention functions, etc.), and "red and black tables" (allocation and switching of attention). Personality structures, features, and types of behavior of operators in stressful situations were estimated basing on adapted QS by Cattell. Mathematical models of the reliability of human nervous system functioning under extreme conditions were developed. Conclusions. The obtained results were taken as the basis for the developed professional selection methods for special contingents, pilots, operators, etc. Physical, mathematical, and program models of the reliability of the human nervous system functioning in these conditions were proposed.

Objeto de memória como categoria de análise de capas de disco

Based on authors from memory, communication, and culture studies, this study discusses the notion of the object of memory as a category in the analysis of long-playing album covers (LP/vinyl) within the relations that involve cultural practices, music, and materialities. As cultural representations shared by artists, record labels, and fans, covers articulate visual memories triggered over time (from the past to the present) by the meanings attributed to them, their presence, and their materiality (wear, imperfections, etc.). This study will observe how some authors treat the term object of memory or surround the notion to reflect on the effectiveness of the category in the analysis of album covers throughout this dialogue.

Investigating the effects of context, visual working memory, and inhibitory control in hybrid visual search.

In real-life scenarios, individuals frequently engage in tasks that involve searching for one of the distinct items stored in memory. This combined process of visual search and memory search is known as hybrid search. To date, most hybrid search studies have been restricted to average observers looking for previously well-memorized targets in blank backgrounds. We investigated the effects of context and the role of memory in hybrid search by modifying the task's memorization phase to occur in all-new single trials. In addition, we aimed to assess how individual differences in visual working memory capacity and inhibitory control influence performance during hybrid search. In an online experiment, 110 participants searched for potential targets in images with and without context. A change detection and go/no-go task were also performed to measure working memory capacity and inhibitory control, respectively. We show that, in target present trials, the main hallmarks of hybrid search remain present, with a linear relationship between reaction time and visual set size and a logarithmic relationship between reaction time and memory set size. These behavioral results can be reproduced by using a simple drift-diffusion model. Finally, working memory capacity did not predict most search performance measures. Inhibitory control, when relationships were significant, could account for only a small portion of the variability in the data. This study provides insights into the effects of context and individual differences on search efficiency and termination.

Dose Response of Transcranial Photobiomodulation on Cognitive Efficiency in Healthy Older Adults: A Task-Related Functional Near-Infrared Spectroscopy Study.

Alzheimer's disease has become increasingly prevalent among the older population, leading to significant social and economic burdens. Transcranial photobiomodulation (tPBM) has shown promise as a cognitive intervention for enhancing cognitive efficiency in healthy older adults, and individuals with mild cognitive impairment and Alzheimer's disease. However, determining the optimal tPBM dosage is crucial for ensuring effective and efficient intervention. This study aimed to compare the effects of different dosages in a single tPBM session on cognitive efficiency in healthy older adults. In this randomized controlled trial, 88 healthy older participants were assigned to either a single dose (irradiance = 30 mW/cm2, fluence = 10.8 J/cm2; n = 44) or a double dose (irradiance = 30 mW/cm2, fluence = 21.6 J/cm2; n = 44) tPBM session. Cognitive efficiency was assessed using functional near-infrared spectroscopy during a visual working memory span task. The single dose group exhibited significantly greater cognitive efficiency enhancement, indicated by a more pronounced reduction in oxygenated hemoglobin during a challenging task level (span level 9) (p = 0.021, d = 0.50), and better working memory task performance (p = 0.045, d = 0.31). Furthermore, participants with better visuospatial abilities demonstrated greater improvement after a single dose (r = -0.42, p = 0.004). In contrast, participants with varying cognitive function did not exhibit additional benefits from a double dose (r = -0.22-0.15, p = 0.16-0.95). These findings suggest that higher tPBM dosages may not necessarily result in superior cognitive improvement in older adults.

Grasp and remember: the impact of human and robotic actions on object preference and memory

Goal contagion, the tendency to adopt others' goals, significantly impacts cognitive processes, which gains particular importance in the emerging field of human–robot interactions. The present study explored how observing human versus robotic actions affects preference and memory. Series of objects undergoing either human or robotic grasping actions together with static (no action) objects were presented, while participants indicated their preference for each object. After a short delay, their memory for grasped, static and new (unstudied) stimuli was tested. Human actions enhanced preference and subsequent recollection of objects, more than robotic actions. In the context of human action, static objects were also perceived as more familiar at recognition. The goal contagion's influence on memory was found to be independent from its impact on preference. These findings highlight the critical role of human interaction in eliciting the impact of goal contagion on cognitive evaluations, memory engagement and the creation of detailed associative memories.

Meaningfulness and Familiarity Expand Visual Working Memory Capacity

Visual working memory is traditionally studied using abstract, meaningless stimuli. Although studies using such simplified stimuli have been insightful in understanding the mechanisms of visual working memory, they also potentially limit our ability to understand how people encode and store conceptually rich and meaningful stimuli in the real world. Recent studies have demonstrated that meaningful and familiar visual stimuli that connect to existing knowledge are better remembered than abstract colors or shapes, indicating that meaning can unlock additional working memory capacity. These findings challenge current models of visual working memory and suggest that its capacity is not fixed but depends on the type of information that is being remembered and, in particular, how that information connects to preexisting knowledge.

The influence of absolute and relative spatial cues on change detection performance

ABSTRACT Two experiments investigate how absolute and relative spatial cues influence perceptual comparisons between visual short-term memory (VSTM) and current vision. The core question concerned the role of task demands in this process. Two tasks were given across two experiments, differing in the extent they required object-level comparisons. Experiment 1, a feature comparison task, required reporting if any new colour was present in the second of two interleaved displays of four colours inside a surround; Experiment 2, an object comparison task, required report of any changes in colour-shape pairings in the second of two interleaved displays of four coloured shapes in a surround. Absolute and relative spatial organization was manipulated in both experiments by presenting compared displays on the same or contralateral sides, and by having the second display items in the same locations within the surround, in new locations, or repositioned into previous locations of other items. In sensitivity, both tasks showed an advantage for absolute spatial cues, but only the object task showed an advantage for relative spatial cues. In bias, both tasks were similarly influenced by both absolute and relative cues. Results suggest relative spatial cues are always available but only used when making object-level comparisons.

Effects of combined postweaning social isolation and ketamine administration on schizophrenia-like behaviour in male Sprague Dawley rats

The pathophysiology behind negative and cognitive symptoms of schizophrenia is not well understood, thus limiting the effectiveness of treatment on these symptoms. Developing reliable animal model of schizophrenia is vital to advance our understanding on the neurobiological basis of the disorder. Double hit is used to refer to the use of two schizophrenia inducing interventions viz ketamine exposure and social isolation. In this study we aim to investigate the robustness of double hit model of schizophrenia in inducing negative and cognitive symptoms of schizophrenia. On postnatal day (PND) 23, thirty-two male Sprague Dawley rats were randomly grouped into four equal groups as follows: group housed + saline (GH), group housed + ketamine (GHK), isolated + saline (SI), and isolated + ketamine (SIK). A single ketamine dose (16 mg/kg) was administered 3 times a week for four weeks. Isolated animals were housed singly throughout the study. The following behavioural tests were carried out: elevated plus maze, three chamber social interaction, resident intruder tests, and novel object recognition (NOR). The SIK group exhibited high anxiety levels, with increased ACTH, corticosterone and norepinephrine concentration when compared to the other groups. The SIK animals also presented with reduced social interaction and decreased oxytocin concentration. SIK rats were more aggressive towards a juvenile intruder but had low testosterone concentration. The SIK group or double hit model showed impaired visual learning and memory and increased expression of proinflammatory cytokines. This suggest that the double hit model is more robust in inducing negative and cognitive symptoms of schizophrenia than each treatment alone.