Extensive lesions of cholinergic basal forebrain neurons do not impair spatial working memory

A recent studysuggests that lesions to all major areas of the cholinergic basal forebrain in the rat (medial septum, horizontal limb of the diagonal band of Broca, and nucleus basalis magnocellularis) impair a spatial working memory task. However, this experiment used a surgical technique that mayhave damaged cerebellar Purkinje cells. The present studytested rats with highlyselective lesions of cholinergic neurons in all major areas of the basal forebrain on a spatial working memorytask in the radial arm maze. In postoperative testing, there were no significant differences between lesion and control groups in working memory, even with a delayperiod of 8 h, with the exception of a transient impairment during the first 2 d of postoperative testing at shorter delays (0 or 2 h). This finding corroborates other results that indicate that the cholinergic basal forebrain does not playa significant role in spatial working memory. Furthermore, it underscores the presence of intact memoryfunctions after cholinergic basal forebrain damage, despite attentional impairments that follow these lesions, demonstrated in other task paradigms.     

Basolateral amygdala inactivation impairs learned (but not innate) fear response in rats

Numerous studies have suggested that the amygdala is involved in the formation of aversive memories, but the possibility that this structure is merely related to any kind of fear sensation or response could not be ruled out in previous studies. The present study investigated the effects of bilateral inactivation of the amygdaloid complex in rats tested in the plus-maze discriminative avoidance task. This task concomitantly evaluates aversive memory (by discrimination of the two enclosed arms) and innate fear (by open-arm exploration). Wistar rats (3-5 months-old) were implanted with bilateral guide cannulae into basolateral amygdala. After surgery, all subjects were given 1 week to recover before behavioral experiments. Afterwards, in experiment 1, 15 min prior to training, 0.5 μl of saline or muscimol (1 mg/ml) was infused in each side via microinjection needles. In experiment 2 the animals received injections immediately after the training session and in experiment 3 rats were injected prior to testing session (24 h after training). The main results showed that (1) pre-training muscimol prevented memory retention (evaluated by aversive arm exploration in the test session), but did not alter innate fear (evaluated by percent time in open arms); (2) post-training muscimol impaired consolidation, inducing increased percent in aversive arm exploration in the test session and (3) pre-testing muscimol did not affect retrieval (evaluated by aversive enclosed arm exploration in the test session). The results suggest that amygdala inactivation specifically modulated the learning of the aversive task, excluding a possible secondary effect of amygdala inactivation on general fear responses. Additionally, our data corroborate the hypothesis that basolateral amygdala is not the specific site of storage of aversive memories, since retention of the previously learned task was not affected by pre-testing inactivation.     

Electrolytic lesions of the medial prefrontal cortex do not interfere with long-term memory of extinction of conditioned fear

Lesion studies indicate that rats without the medial prefrontal cortex (mPFC) have difficulty recalling fear extinction acquired the previous day. Several electrophysiological studies have also supported this observation by demonstrating that extinction-related increases in neuronal activity in the mPFC participate in expression of fear extinction. However, a more recent study has shown that fear extinction can be recalled, in certain circumstances, without mPFC potentiation, suggesting contribution of other circuits. Here, we examined this possibility in rats that were subjected to auditory fear conditioning, extinction training, and extinction retention test 7 d later. Electrolytic lesions were made in the mPFC, the motor cortex (MO), the dorsal septum (SEP), or the mediodorsal thalamus (MD), because of their potential participation in conditioned fear inhibition; combined lesions including the mPFC with the MO, SEP, or MD were also made. The lesions were made either 1 wk before conditioning or 1 d after extinction training. All rats normally extinguished their conditioned freezing behavior during extinction training and did not display any return of this behavior during the retention test. These data reveal that the mPFC is not required for the acquisition, the expression, or the retrieval of extinction memories but do not exclude the possibility that the mPFC normally participates in these processes.     

Basolateral amygdala noradrenergic activity mediates corticosterone-induced enhancement of auditory fear conditioning

The present experiment examined whether posttraining noradrenergic activity within the basolateral complex of the amygdala (BLA) is required for mediating the facilitating effects of acutely administered glucocorticoids on memory for auditory-cue classical fear conditioning. Male Sprague-Dawley rats received five pairings of a single-frequency auditory stimulus and footshock, followed immediately by bilateral infusions of the beta1-adrenoceptor antagonist atenolol (0.5 microg in 0.2 microl) or saline into the BLA together with a subcutaneous injection of either corticosterone (3.0 mg/kg) or vehicle. Retention was tested 24 h later in a novel test chamber and suppression of ongoing motor behavior served as the measure of conditioned fear. Corticosterone facilitated memory as assessed by suppression of motor activity during the 10-s presentation of the auditory stimulus and intra-BLA administration of atenolol selectively blocked this corticosterone-induced memory enhancement. These findings provide evidence that, as found with other emotionally arousing tasks, the enhancing effects of corticosterone on memory consolidation of auditory-cue fear conditioning require posttraining noradrenergic activity within the BLA.     

Visual short-term memory is not improved by training

A critical question in visual working or short-term memory (VSTM) research is whether the ability to remember briefly presented visual stimuli can be increased. Here we test whether VSTM for locations and shapes is improved by training that allows one to utilize another memory system, visual longterm memory (VLTM). Training was done by repeatedly presenting a subset of memory displays, creating long-term memory traces for these displays. Surprisingly, VSTM performance for repeated displays was not higher than for nonrepeated ones, even though participants recognized repeated displays on a forced-choice test given at the end of the experiment. We suggest that the fidelity of information held by VLTM is inferior to that of information held by VSTM and thus provides no additional benefit over what is extracted on the fly by VSTM.     

Performance gains from directed training do not transfer to untrained tasks

Given the increasing complexity of the tasks and skills needed in modern society, developing effective training strategies is of tremendous practical importance. Furthermore, training that improves performance of both trained and untrained tasks would be highly efficient. In the present study, we examined how directed training contributes to skill acquisition, and more importantly, to engendering transfer of training to untrained tasks. Participants learned a complex video game for 30 h (Space Fortress, Donchin, Fabiani, & Sanders, 1989) using one of two training regimens: Hybrid Variable-Priority Training (HVT), with a focus on improving specific skills and managing task priority, or Full Emphasis Training (FET) in which participants simply practiced the game to obtain the highest overall score. We compared game performance, retention of training gains, and transfer of training to untrained tasks as a function of the training regimen. Compared to FET, HVT learners reached higher levels of mastery on the game and HVT was particularly beneficial for initially poor performing participants. This benefit persisted seven months after training. However, contrary to expectation, both HVT and FET were unsuccessful in producing transfer to untrained tasks compared to a group that received limited game experience, suggesting that directed training and practice can produce task-specific improvements, but improvements do not necessarily transfer from trained to untrained tasks.     

State-dependent memory effects using caffeine and placebo do not extend to metamemory

The authors examined the impact of caffeine on human memory and predictions of memory (i.e., metamemory). On Day 1, 83 college students drank a sweetened beverage containing either caffeine (4 mg/kg body weight) or a placebo before they studied 40 pairs of words. While the participants studied, they predicted their future memory performance for each word pair. On Day 2, the participants again received caffeine or a placebo before the memory test. The participants who drank the same beverage on both days (either caffeine or a placebo) recalled more word pairs than did those who drank different beverages (caffeine on 1 day and a placebo on the other day). In contrast, memory predictions were more accurate when the beverages did not match on both days. These data provide evidence for state-dependent memory when caffeine is used, but not for state-dependent metamemory. People's memory and their predictions of memory can be influenced in different ways if they drink caffeine before they study or take a test.     

Forgotten but not gone: context effects on recognition do not require explicit memory for context

Context effects on recognition memory provide an important indirect assay of associative learning and source memory. Neuropsychological studies have indicated that such context effects may obtain even if the contexts themselves are not remembered--for example, in individuals impaired on direct tests of memory for contextual information. In contrast, a recent study indicated that the effects of temporal context reinstatement on visual recognition obtain only when the contextual information itself was explicitly recollected. Here we report that the effects of reinstatement of spatial-simultaneous context on visual object recognition memory obtain irrespective of whether those context stimuli are explicitly recognized. We suggest that spatial-simultaneous context effects might be based on ensemble unitization of target and context stimuli at encoding, whereas temporal context effects may require recollective processes.     

Forgotten but not gone: Context effects on recognition do not require explicit memory for context

Context effects on recognition memory provide an important indirect assay of associative learning and source memory. Neuropsychological studies have indicated that such context effects may obtain even if the contexts themselves are not remembered—for example, in individuals impaired on direct tests of memory for contextual information. In contrast, a recent study indicated that the effects of temporal context reinstatement on visual recognition obtain only when the contextual information itself was explicitly recollected. Here we report that the effects of reinstatement of spatial-simultaneous context on visual object recognition memory obtain irrespective of whether those context stimuli are explicitly recognized. We suggest that spatial-simultaneous context effects might be based on ensemble unitization of target and context stimuli at encoding, whereas temporal context effects may require recollective processes.     

Inferior temporal lesions do not impair discrimination of rotated patterns in monkeys.

Ablation of inferior temporal cortex in the rhesus monkey produces a visual discrimination learning deficit. The severity of this deficit has often been found to be a function of task difficulty. This report concerns a type of visual discrimination problem that, although difficult, is not sensitive to inferior temporal lesions. Monkeys with anterior, posterior, and complete inferior temporal lesions were repeatedly unimpaired or only slightly impaired in learning to discriminate a pattern from the same pattern rotated 90 degrees or 180 degrees; yet they were very severely impaired in learning equally or more difficult discriminations of two different patterns. This demonstration that discrimination of orientation of patterns is relatively spared after inferior temporal lesions helps specify the pattern-recognition processes that require inferior temporal cortex.     

Prefrontal cortex or basolateral amygdala lesions blocked the stress-induced inversion of serial memory retrieval pattern in mice

Previous data from our team have shown that pre-test stress in mice reversed the pattern of memory retrieval in a contextual serial spatial task (CSD; Celerier, A., Pierard, C., Rachbauer, D., Sarrieau, A., & Beracochea, D. (2004). Contextual and serial discriminations: A new learning paradigm to assess simultaneously the effects of acute stress on retrieval of flexible or stable information in mice. Learning and Memory, 11, 196-204). The present study is aimed at determining brain areas which might be critically involved in mediating the stress effect on memory retrieval in the CSD task. For that purpose, we studied hereby the effects of ibotenic acid lesions of either the prefrontal cortex (PFC) or the basolateral amygdala (BLA) in Stressed or Non-Stressed Balb/c mice on memory retrieval in the CSD task. In that task, mice learned two successive spatial discriminations (D1 and D2) within two different internal contexts in a four-hole board. The stressor (electric footshocks) was delivered 5 min before test, occurring 24 h after acquisition. During test, mice were relocated either on the floor of the first or of the second discrimination. Results showed that (i) spatial memory was substantial and remained unaffected both by lesions and stress; (ii) Non-Stressed controls as well as Non-Stressed or Stressed PFC and BLA-lesioned mice remembered accurately D1 but not D2; and (iii) in contrast, Stressed controls accurately remembered D2 but not D1. In parallel to behavioral experiments, we also showed that PFC and BLA lesions did not affect the stress-induced increase of plasma corticosterone levels. All together, PFC and BLA integrity are not necessary for retrieval processes per se; in contrast, the PFC and BLA are critically involved in the mediation of the deleterious stress effects on serial order memory retrieval.     

Payment schedules do not affect attendance/completion of group behavioral parent training

Though previous research suggests that attendance at individual therapy is not impacted by amount or source of payment for services, such research is relatively sparse and clinician concerns remain. The present study explores the connection between payment of fees and attendance at group treatments--a previously unexplored area. Participants in a 10-week behavioral parent training (BPT) program varied in timing of payment of fees as well as amount of fees based on income. The varying payment schedules did not affect attendance to sessions at which payments were due nor did payment schedules affect completion of the program. A small relationship was found between income group and attendance. The results are discussed in their relation to the larger literature on fees and attendance at psychotherapy.     

Prospective memory training in young adults enhances trained-task but not transfer-task performance

ABSTRACT

Training and transfer effects of prospective memory training have not been assessed in healthy young adults yet. The present study examined the effects of an 8-day prospective memory training programme using the Virtual Week computer game in 18–24-year-old students. Using the performance of an active control group as comparison, the study revealed a significant short-lived beneficial training-induced effect on a nearest-transfer task consisting of a different version of the trained task. No evidence was obtained for transfer effects to other tasks measuring prospective memory (near transfer), or to tasks measuring various executive functions or general intelligence (far transfer). These results were compared to those from a previous study in which an identical training and testing protocol was used in 13–15-year-old adolescents. This study did reveal some evidence of near and far transfer. The results of the two studies combined suggest a greater potential for prospective memory training to induce beneficial transfer effects in young adolescents than in young adults.     

Basolateral amygdala noradrenergic activity is involved in the acquisition of conditioned odor aversion in the rat

Conditioned odor aversion (COA) is the avoidance of an odorized-tasteless solution (the conditioned stimulus, CS), the ingestion of which precedes toxicosis. Previous works have shown that the basolateral nucleus of the amygdala (BLA) is involved in the acquisition, and more precisely, the control of the CS memory trace, of COA. Since catecholamine depletion of the amygdala induced a deficit in the potentiated version of COA, this study investigated the role of the adrenergic system in the BLA during COA. Male Wistar rats bilaterally implanted with cannulae aimed at the BLA were microinjected with the beta-adrenergic antagonist propranolol (1 microg/0.2 microl) during the acquisition (5 min before the CS presentation, pre-CS, or immediately after, post-CS) or during the retrieval test (5 min before test, pre-test). Results showed that pre-CS, but neither post-CS nor pre-test, infusions of propranolol impaired COA, suggesting that beta-adrenergic system activity in the BLA is involved in the acquisition but not the expression of COA. Moreover, the fact that pre-CS, but not post-CS, treatment disrupted COA suggests that beta-adrenergic system in the BLA is involved in the initiation but not the maintenance of the CS memory trace during COA acquisition.     

Impaired emotional declarative memory following unilateral amygdala damage

Case studies of patients with bilateral amygdala damage and functional imaging studies of normal individuals have demonstrated that the amygdala plays a critical role in encoding emotionally arousing stimuli into long-term declarative memory. However, several issues remain poorly understood: the separate roles of left and right amygdala, the time course over which the amygdala participates in memory consolidation, and the type of knowledge structures it helps consolidate. We investigated these questions in eight subjects with unilateral amygdala damage, using several different measures. For comparison, our main task used stimuli identical to those used previously to investigate emotional declarative memory in patients with bilateral amygdala damage. Contrasts with both brain-damaged and normal control groups showed that subjects with left amygdala damage were impaired in their memory for emotional stimuli, despite entirely normal memory for neutral stimuli (because of a number of caveats, the findings from subjects with right amygdala damage were less clear). Follow-up experiments suggested that the normal facilitation of memory for emotional stimuli may develop over an extended time course (>30 min), consistent with prior findings, and that the specific impairment we report may depend in part on the lexical nature of the task used (written questionnaire). We stress the complex and temporally extended nature of memory consolidation and suggest that the amygdala may influence specific components of this process.     

Language differences in verbal short-term memory do not exclusively originate in the process of subvocal rehearsal

Language differences in verbal short-term memory were investigated in two experiments. In Experiment 1, bilinguals with high competence in English and French and monolingual English adults with extremely limited knowledge of French were assessed on their serial recall of words and nonwords in both languages. In all cases recall accuracy was superior in the language with which individuals were most familiar, a first-language advantage that remained when variation due to differential rates of articulation in the two languages was taken into account. In Experiment 2, bilinguals recalled lists of English and French words with and without concurrent articulatory suppression. First-language superiority persisted under suppression, suggesting that the language differences in recall accuracy were not attributable to slower rates of subvocal rehearsal in the less familiar language. The findings indicate that language-specific differences in verbal short-term memory do not exclusively originate in the subvocal rehearsal process. It is suggested that one source of language-specific variation might relate to the use of long-term knowledge to support short-term memory performance.