Productive and defective impairments in the neglect syndrome: graphic perseveration, drawing productions and optic prism exposure

The effects of adaptation to prisms displacing rightwards the field of vision on omission errors, and on perseveration and other graphic productions in a line cancellation task, were assessed in nine right-brain-damaged patients with left unilateral spatial neglect. Prism adaptation improved both neglect, as indexed by omission errors, and perseveration behaviour, up to a delay of 60 min. No correlation was found between omission and perseveration errors in all assessments. The suggestion is made that perseveration and other complex graphic productions made by right brain-damaged-patients with left spatial unilateral neglect is due to a defective monitoring of complex motor behaviour, frequently associated to cerebral damage involving the right frontal lobe. Interpretations of perseveration behaviour in terms of allochiria and directional hypokinesia are considered, and their limits discussed.     

Aberrant cortico–subcortical functional connectivity among women with poor motor control: Toward uncovering the substrate of hyperkinetic perseveration

Objective

Hyperkinetic perseveration (HKP) refers to perseverative repetition of rudimentary motor output. Although HKP is known to be associated with brain injuries and certain neurodegenerative disorders (primarily those involving the frontal lobes and the basal ganglia), an increased tendency to exhibit HKP is also commonly associated with apparently normal aging (i.e., in the absence of known neuropathology). The purpose of the present study was to examine anomalies in brain functioning associated with HKP tendencies in a non-injured brain.

Method

The present study examined functional MRI connectivity patterns associated with HKP in a sample of 24 “young” (ages 25–35 years) and 20 “old” (ages 65–75 years) healthy community dwelling women. Participants performed a motor learning task (the Push-Turn-Taptap task: PTT) known to elicit HKP. On a separate day, participants were scanned on a Siemens 3T Trio MR scanner with a 12-channel head coil, while performing a block-design motor sequence learning task that was designed to be a scanner analog for the PTT task. Cortico–subcortical connectivity patterns involving two subcortical regions of interest (putamen and thalamus) and three cortical regions (sensory-motor cortex, Brodmann Area 6, inferior frontal gyrus) were examined.

Results

Older participants exhibited a higher rate of HKP compared to younger participants. Age-related HKP was associated with hemispheric asymmetry marked by a relatively stronger right-hemisphere cortico–subcortical connectivity involving the sensory-motor cortex and, to a lesser extent, Brodmann Area 6. These patterns were distinct from connectivity patterns associated with aging alone.

Conclusions

HKP is related to anomalies involving frontal–subcortical circuits. Future research should examine specific components of the basal-ganglia circuitry.     

BMY 21502 and piracetam facilitate performance of two-choice win-stay water-escape in normal rats

Summary Sprague-Dawley rats given either 5 or 10 mg/kg of a new compound, BMY 21502, 150 mg/kg of piracetam or a dose of methylcellulose vehicle (p.o.) daily for 38 days beginning two days before training were compared on performance of a win-stay water-escape task in a circular water maze requiring the use of working memory. The task involved giving the rats pairs of trials in which the location of a submerged escape platform remained the same within a pair of trials but changed semirandomly across pairs. Rats receiving either 5 mg/kg BMY 21502 or piracetam made more correct choices than did rats receiving only the vehicle (p<0.05 in each case). The facilitated performance was associated with making fewer perseverative responses that resulted in errors.Supported in part by a grant from Bristol-Myers to LWM.     

Septal lesions and hyperdipsia in the Mongolian gerbil.

Mongolian gerbils (Meriones unguiculatus) were subjected to anterior septal lesions. Lesions involved primarily the septal and parolfactorial areas bilaterally. Following the lesions, gerbils became hyperdipsic compared to previously obtained baseline measurements. Lesioned animals also showed prolonged water ingestions following the injection of hyperoncotic solutions compared both to non-lesioned controls and their own preoperative responses. Finally, results indicate that response inhibition following septal lesions in gerbils seems unimpaired as differential-reinforcement of-low-rate response performance was at preoperative levels. These results suggest that portions of the septal area of the gerbil forebrain function in a similar manner to that reported in the white rat.     

Effect of a physical barrier on response perseveration in hippocampal lesioned rats

Hippocampal lesioned and sham operated rats were required to relearn entry into a previously learned reinforced side arm in a T-maze from a new starting position 180 degrees from the original location. Half of each operated group were allowed free access while the other half had to open clear plastic doors to gain entry into the side arms. Only those hippocampal lesioned rats allowed free access to the side arms failed to relearn the entry response in fewer errors or with significant slower running speed than in the initial task. Both sham operated subgroups and the obstructed hippocampal lesioned group of rats learned the second task in fewer errors and displayed running speed disruption. The results were discussed in terms of a deficit of internal inhibition due to the limbic damage.     

Repetitive verbalization in Alzheimer’s disease

Background: Repetitive verbalization in Alzheimer’s disease (AD) refers to the tendency of AD patients to repeat the same story/question to the same listener.

Aim: Our study assessed whether this verbal perseveration might be related to episodic memory decline, values of teaching, inhibitory decline, and/or decline in cognitive theory of mind.

Methods & Procedures: Thirty mild AD patients and 33 control older adults were asked to perform four verbal fluency tasks, and repeated words were retained as an index of repetitive verbalization. Participants were also administered the Grober and Buschke episodic memory task, scales of values of teaching, the Hayling inhibition task, and the false-belief task for the cognitive theory of mind.

Outcomes & Results: Results showed more repetitive verbalization in AD patients than in control older adults. Repetitive verbalization was significantly correlated with inhibition and episodic memory in AD patients. As for control older adults, repetitive verbalization was significantly correlated with values of teaching and inhibition. Regression analyses showed that repetitive verbalization was significantly predicted by inhibition in AD patients and values of teaching in control older adults.

Conclusions: Repetitive verbalization may reflect the difficulty in inhibiting irrelevant stimuli in AD patients, but it may serve as a tool to ensure transmission of personal knowledge in normal aging. Our findings suggest distinct functions of repetitive verbalization in normal aging and AD.     

Action-selection perseveration in young children: Advances of a dynamic model

This study presents an empirical test and dynamic model of perseverative limb selection in children of 14-, 24-, and 36-months old (N = 66 in total). In the experiment, children repeatedly grasped a spoon with a single hand. In two separate conditions, the spoon was presented either four times on their right side or four times on their left side. In both conditions, following this training, the spoon was presented on midline for two more trials. This setup enabled us to determine whether children's limb selection was influenced by their prior choices in the task (i.e., perseveration). Individual children's handedness was determined in a third condition consisting of nine object presentations (laterally or on midline). A dynamic model for limb selection is presented combining external input, motor memory, and preferences. The model was used to simulate the experiment and reproduced the results, including the age-related changes.     

Attentional dysfunction of the central executive in AD: evidence from dual task and perseveration errors

This study examined the capacity of 27 Alzheimer's disease (AD) patients to divide attention between two simultaneous tasks, as compared to 27 elderly controls. In order to determine whether distribution of attention is affected by age, a younger group was included. The results showed a marked impairment in the capacity of the AD patients to combine performance in two simultaneous tasks compared to the elderly controls, but the latter group did not differ from the younger participants, indicating a disease rather than an age effect, and replicating the results of Baddeley et al. (2001). The present study also analysed whether perseverations committed in a previous study (Sebastian et al., 2001) by some AD and elderly control participants in the Brown-Peterson (B-P) task (Brown, 1958; Peterson and Peterson, 1959) were related to their attentional capacity in the dual task. Although the elderly controls committed perseveration errors, a negative correlation was only found in the AD group between the index of attention distribution in the dual task and the frequency of perseverations in the B-P task. Our results would therefore suggest that AD patients show a dysfunction of the central executive and/or a deficit in their ability to allocate cognitive resources. This could be interpreted in terms of problems in updating the contents of working memory and suppressing activation of no-longer-relevant information in the early stages of AD, leading to perseveration errors in the B-P task.     

Valproate attenuates hyperactive and perseverative behaviors in mutant mice with a dysregulated dopamine system.

BACKGROUND: Dopamine transporter (DAT) knockdown (KD) mice, with approximately 90% loss of expression of the DAT, allow for the examination of the behavioral consequences of a chronically dysregulated dopamine system. The DAT KD mice have hyperdopaminergic tone, are hyperactive, and show impaired response inhibition in a number of paradigms. We hypothesized that the DAT KD mice would also display deficits in prepulse inhibition (PPI) and would be perseverative in their locomotor behavior. METHODS: Basal levels of PPI and patterns of locomotor behavior were measured in two cohorts of DAT KD mice. In addition, measurements of locomotor behavior were recorded after pretreatment with 100 mg/kg valproate in both DAT KD and wildtype mice. RESULTS: The DAT KD mice were hyperactive and displayed perseverative motor behavior but had normal levels of PPI. The clinically effective antimania drug valproate significantly attenuated the hyperactivity and perseverative locomotor behavior in the DAT KD mice and had no effect in control mice. CONCLUSIONS: The DAT KD mice appear to provide a model of some aspects of manic behavior. With limited models of bipolar disorder, the DAT KD mice might provide a vehicle to screen for new psychiatric therapies to treat mania and its related symptoms.