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PubMed2001

CA1-specific N-methyl-D-aspartate receptor knockout mice are deficient in solving a nonspatial transverse patterning task.

In both humans and animals, the hippocampus is critical to memory across modalities of information (e.g., spatial and nonspatial memory) and plays a critical role in the organization and flexible expression of memories. Recent studies have advanced our understanding of cellular basis of hippocampal function, showing that N-methyl-d-aspartate (NMDA) receptors in area CA1 are required in both the spatial and nonspatial domains of learning. Here we examined whether CA1 NMDA receptors are specifically required for the acquisition and flexible expression of nonspatial memory. Mice lacking CA1 NMDA receptors were impaired in solving a transverse patterning problem that required the simultaneous acquisition of three overlapping odor discriminations, and their impairment was related to an abnormal strategy by which they failed to adequately sample and compare the critical odor stimuli. By contrast, they performed normally, and used normal stimulus sampling strategies, in the concurrent learning of three nonoverlapping concurrent odor discriminations. These results suggest that CA1 NMDA receptors play a crucial role in the encoding and flexible expression of stimulus relations in nonspatial memory.

Animals↗

PubMed2005

Seahorse wins all races: hippocampus participates in both linear and non-linear visual discrimination learning.

Consistent with configural/conjunctive theories of the hippocampus, we report that rats trained on the non-linear transverse patterning discrimination problem (A+ versus B-, B+ versus C-, and C+ versus A) displayed retrograde amnesia when the hippocampus was later damaged. They also failed to relearn the solution to this problem. Damage to the hippocampus following training also produced retrograde amnesia in rats trained on a set of elemental discrimination problems (A+ versus B-, C+ versus D-, and E+ versus F-) that could be solved based on the associative strengths of the individual choice cues. However, in contrast to transverse patterning, rats easily relearned and retained these elemental problems and learned a new set of elemental problems after the damage. These results support two theoretical conclusions: (a) elemental discriminations can be learned by both a system that depends on the hippocampus and a system that does not require the hippocampus, and (b) in the intact animal these two systems competitively interact with the hippocampal-dependent system inhibiting memory formation by the extra-hippocampal system.

Animals↗

PubMed1996

The neuropsychological profile of cri du chat syndrome without significant learning disability.

The clinical picture typically associated with cri du chat syndrome is one of profound intellectual impairment, severe motor delay and increased morbidity. In contrast to this picture, the present case report describes the cognitive and behavioural profile of a young female with cri du chat syndrome who displays no evidence of severe learning disability. Cognitive performance indicated good verbal skills with specific strengths on those tasks that require the ability to store and retrieve verbal information in comparison to poor non-verbal, spatial skills and weaknesses on those tasks that require multi-step manipulation of spatial stimuli and the ability to form whole percepts from fragmentary parts. The finding underlies the importance of assessing the wide range of cognitive potential of individuals with cri du chat syndrome.

Child↗

PubMed2005

Silent synapses in a thalamo-cortical circuit necessary for song learning in zebra finches.

Developmental changes in synaptic properties may act to limit neural and behavioral plasticity associated with sensitive periods. This study characterized synaptic maturation in a glutamatergic thalamo-cortical pathway that is necessary for vocal learning in songbirds. Lesions of the projection from medial dorsolateral nucleus of the thalamus (DLM) to the cortical nucleus lateral magnocellular nucleus of the anterior nidopallium (LMAN) greatly disrupt song behavior in juvenile birds during early stages of vocal learning. However, such lesions lose the ability to disrupt vocal behavior in normal birds at 60-70 days of age, around the time that selective auditory tuning for each bird's own song (BOS) emerges in LMAN neurons. This pattern has suggested that LMAN is involved in processing song-related information and evaluating the degree to which vocal motor output matches the tutor song to be learned. Analysis of reversed excitatory postsynaptic currents at DLM-->LMAN synapses in in vitro slice preparations revealed a pronounced N-methyl-D-aspartate receptor (NMDAR)-mediated component in both juvenile and adult cells with no developmental decrease in the relative contribution of NMDARs to synaptic transmission. However, the synaptic failure rate at DLM-->LMAN synapses in juvenile males during the sensitive period for song learning was significantly lower at depolarized potentials than at hyperpolarized potentials. In contrast, the failure rate at DLM-->LMAN synapses did not differ at hyper- versus depolarized holding potentials in adult males that had completed the acquisition of a stereotyped song. This pattern indicates that juvenile cells have a higher incidence of silent (NMDAR-only) synapses, which are postsynaptically silent at hyperpolarized potentials due to the voltage-dependent gating of NMDARs. Thus the decreased involvement of the LMAN pathway in vocal behavior is mirrored by a decline in the incidence of silent synapses but not by changes in the relative number of NMDA and AMPA receptors at DLM-->LMAN synapses. These findings suggest that a developmental decrease in silent synapses within LMAN may represent a neural correlate of behavioral plasticity during song learning.

Age Factors↗

PubMedDate not supplied

AAPM/RSNA physics tutorial for residents: fundamental physics of MR imaging.

Learning the basic concepts required to understand magnetic resonance (MR) imaging is a straightforward process. Although the individual concepts are simple, there are many concepts to learn and retain simultaneously; this situation may give the illusion that learning the physics of MR imaging is complicated. It is important for the radiologist who interprets MR images to understand the methods used to create the images because image contrast specifically depends on how the image data were acquired. Initial concepts include formation of magnetic fields from electric currents in loops of wire, the resonance phenomenon, the hydrogen proton and its frequency of precession, and absorption of radiofrequency energy. These concepts can then be applied to learn about T1 and T2 relaxation and contrast and how the acquisition parameters of echo time and repetition time can be used to achieve these image contrasts. Basic pulse sequences include the spin-echo, multiecho spin-echo, turbo spin-echo, inversion-recovery, and gradient-recalled-echo sequences.

Internship and Residency↗

PubMed1996

Learning disabilities, low achievement, and mild mental retardation: more alike than different?

Children identified with learning disabilities (LD), low achievement (LA), or mild mental retardation (MMR) were contrasted on 41 measures of ability, academic achievement, social skills, problem behavior, academic engaged time, perceptual-motor skills, and school history. Both multivariate, univariate, and meta-analytic comparisons among the three groups showed relatively large differences on measures of aptitude and achievement, with the LD group scoring higher on measures of cognitive ability than the LA and MMR groups and the LA group showing higher tested academic achievement than the LD and MMR groups. Teacher ratings of academic competence showed similar levels of functioning for the LD and LA groups. No differences among the groups were found on measures of social skills, problem behaviors, or academic engaged time, or on most indices reflecting school history. Results were interpreted in light of studies contrasting LD and LA groups. Comparisons with earlier studies were difficult in light of demographic differences in samples and the lower cognitive and academic functioning of children in the present study. The current study showed that 61% of the LD group could be differentiated from the LA group, with LD-MMR and LA-MMR differentiation levels being 68.5% and 67.5%, respectively.

Child↗

PubMed2003

Hippocampal lesions and discrimination performance of mice in the radial maze: sparing or impairment depending on the representational demands of the task.

The effects of ibotenate hippocampal lesions on discrimination performance in an eight-arm radial maze were investigated in mice, using a three-stage paradigm in which the only parameter that varied among stages was the way the arms were presented. In the initial learning phase (stage 1), animals learned the valence or reward contingency associated with six (three positive and three negative) adjacent arms of the maze using a successive (go/no-go) discrimination procedure. In the first test phase (stage 2), the six arms were grouped into three pairs, so that on each trial, the subject was faced with a choice between two adjacent arms of opposite valence (concurrent two-choice discrimination). In the second test phase (stage 3), the subject was faced with all six arms simultaneously (six-choice discrimination). Hippocampal-lesioned mice acquired the initial learning phase at a near-normal rate but behaved as if they had learned nothing when challenged with the two-choice discriminations at stage 2. In contrast, they behaved normally when confronted with the six-choice discrimination at stage 3. Detailed examination of within- and between-stage performance suggests that hippocampal-lesioned mice perform as intact mice when presentation of the discriminanda encourages the storage and use of separate representations (i.e., in initial learning and six-choice discrimination testing), but that they fail in test situations that involve explicit comparisons between such separate representations (two-choice discriminations), hence requiring the use of relational representations.

Algorithms↗

PubMedDate not supplied

Parallel brain systems for learning with and without awareness.

A fundamental issue about memory and its different forms is whether learning can occur without the development of conscious knowledge of what is learned. Amnesic patients and control subjects performed a serial reaction time task, exhibiting equivalent learning of an imbedded repeating sequence as measured by gradually improving reaction times. In contrast, four tests of declarative (explicit) knowledge indicated that the amnesic patients were unaware of their knowledge. Moreover, after taking the tests of declarative memory, all subjects continued to demonstrate tacit knowledge of the repeating sequence. This dissociation between declarative and nondeclarative knowledge indicates that the parallel brain systems supporting learning and memory differ in their capacity for affording awareness of what is learned.

Aged↗

PubMed2002

Perceptual learning of temporal structure.

We investigated the extent to which the ability to perceive spatial form from temporal structure (TS) improves with practice. Observers trained monocularly for a number of consecutive days on a shape discrimination task, with one group of observers judging shape defined by luminance contrast between target and background elements and another group judging shape defined by correlated TS (synchronized changes in motion direction between target and background elements). Substantial learning was found for both shape tasks, with complete interocular transfer of training. Observers trained on TS showed no transfer of learning to the luminance condition, but observers trained using the luminance display with incidental synchronized changes did show transfer to the TS task. Possible underlying neural changes are discussed.

Contrast Sensitivity↗

PubMed1987

Effects of chronic diisopropylfluorophosphate treatment on spatial learning in mice.

The Morris water task was used to measure the effects of chronic diisopropylfluorophosphate (DFP) treatment on C57BL/6Ibg mice. Control mice showed good task acquisition and searched accurately for the platform after it was removed from the pool, suggesting that they had formed a spatial map of the platform's location relative to distal cues. In contrast, mice chronically treated with DFP prior to training showed a marked deficit in spatial learning. Chronic DFP treatment did not affect ability to locate a visible platform and did not impair task retention in mice trained to find the hidden platform prior to DFP treatment. The chronic DFP treatment decreased muscarinic binding in cortex, hippocampus, and striatum. These results indicate that C57BL mice are capable of spatial learning in the water task. The ability of chronic DFP treatment to impair place but not cue learning suggests that the cholinergic dysfunction produced by DFP is similar to those produced by lesions of central cholinergic systems and acute treatments with muscarinic antagonists.

Animals↗

PubMed2006

The role of mechanosensory input in flower handling efficiency and learning by Manduca sexta.

Nectar-foraging animals are known to utilize nectar guides-- patterns of visual contrast in flowers-- to find hidden nectar. However, few studies have explored the potential for mechanosensory cues to function as nectar guides, particularly for nocturnal pollinators such as the tobacco hornworm moth, Manduca sexta. We used arrays of artificial flowers to investigate the flower handling behavior (the ability to locate and drink from floral nectaries) of naïve moths, looking specifically at: (1) how the shape and size of flat (two-dimensional) artificial corollas affect nectar discovery and (2) whether three-dimensional features of the corolla can be used to facilitate nectar discovery. In these experiments, we decoupled visual from tactile flower features to explore the role of mechanosensory input, putatively attained via the extended proboscides of hovering moths. In addition, we examined changes in nectar discovery times within single foraging bouts to test whether moths can learn to handle different kinds of artificial flowers. We found that corolla surface area negatively affects flower handling efficiency, and that reliable mechanosensory input is crucial for the moths' performance. We also found that three-dimensional features of the corolla, such as grooves, can significantly affect the foraging behavior, both positively (when grooves converge to the nectary) and negatively (when grooves are unnaturally oriented). Lastly, we observed that moths can decrease nectar discovery time during a single foraging bout. This apparent learning ability seems to be possible only when reliable mechanosensory input is available.

Animals↗

PubMed2004

Amphetamine decreases the expression and acquisition of appetitive conditioning but increases the acquisition of anticipatory responding over a trace interval.

The effects of amphetamine on selective learning were tested in a trace conditioning procedure, in which the informativeness of the conditioned stimulus (CS) (noise) was manipulated through the introduction of a time interval before the delivery of the unconditioned stimulus (UCS) (food). The results showed that d-amphetamine (0.5 and 1.5 mg/kg) impaired both the expression (Experiment 1b) and acquisition (Experiment 2) of appetitive conditioning. This was true for both trace and contiguously conditioned groups. The effects of the 0.5 mg/kg dose of d-amphetamine were not attributable to general motor (measured pre-CS) or motivational (measured post-UCS) effects of the drug. Moreover, the same pattern of effects (impaired appetitive conditioning, irrespective of the trace interval between CS and UCS) was confirmed in drug-free extinction tests. By contrast to the general depression in the acquisition and expression of associative learning observed under amphetamine, the 0.5 mg/kg dose promoted the acquisition of anticipatory responses made later in the trace interval (in Experiment 2 but, again, not the expression of previous conditioning in Experiment 1b). This suggests a dissociable effect of low-dose d-amphetamine on learning about the temporal relationship between CS and UCS.

Acoustic Stimulation↗

PubMed2001

The relationship of work avoidance and learning goals to perceived competence, externality and meaning.

BACKGROUND: Motivational researchers have suggested that work avoidance may be an academic goal in which students seek to minimise the amount of work they do in school. Additionally, research has also suggested that emotions may be catalysts for goals. AIM: This study examined the relationship between emotions and learning or work avoidance goals. Do emotions explain goals? SAMPLE: The participants were 512 senior high school students in Eastern Canada. METHOD: Students completed a survey assessing motivation related constructs. A structural equation model was postulated in which students' affect predicted learning goals and work avoidant goals. A cluster analysis of affect scores was performed followed by between-group and within-group contrasts of goal scores. RESULTS: The structural equation model suggested that a sense of competence and control were predictive of a learning goal while lack of meaning was related to work avoidance. The cluster analysis showed that confidence and control were associated with a learning goal but that a sense of inadequacy, lack of control or lack of meaning could give rise to work avoidance. CONCLUSIONS: Emotions seem to be directly linked to goals. Teachers who foster feelings of self-assuredness will be helping students develop learning goals. Students who feel less competent, bored or have little control will adopt work avoidant goals.

Adolescent↗

PubMed2006

Lectures are such an effective teaching method because they exploit evolved human psychology to improve learning.

Lectures are probably the best teaching method for many students in many circumstances; especially for communicating conceptual knowledge, and where there is a significant knowledge gap between lecturer and audience. However, the lack of a convincing rationale has been a factor in under-estimating the importance of lectures, and there are many who advocate their replacement with written communications or electronic media. I suggest that lectures are so effective because they exploit the spontaneous human aptitude for learning from spoken (rather than written) information. Literacy is a recent cultural artefact, and for most of their evolutionary history humans communicated by direct speech. By contrast with speech, all communication technologies--whether reading a book or a computer monitor--are artificial and unnatural. Furthermore, learning is easier during formal, quiet, real-time social events. The structure of a lecture artificially manipulates human psychology to increase vigilance, focus attention, and generate authority for the lecturer--all of which make communications more memorable for the student. Instead of trying to phase-out lectures, we should strive to make them better by understanding that lectures are essentially formal, spoken, social events.

Humans↗

PubMed1999

Neural encoding in orbitofrontal cortex and basolateral amygdala during olfactory discrimination learning.

Orbitofrontal cortex (OFC) is part of a network of structures involved in adaptive behavior and decision making. Interconnections between OFC and basolateral amygdala (ABL) may be critical for encoding the motivational significance of stimuli used to guide behavior. Indeed, much research indicates that neurons in OFC and ABL fire selectively to cues based on their associative significance. In the current study recordings were made in each region within a behavioral paradigm that allowed comparison of the development of associative encoding over the course of learning. In each recording session, rats were presented with novel odors that were informative about the outcome of making a response and had to learn to withhold a response after sampling an odor that signaled a negative outcome. In some cases, reversal training was performed in the same session as the initial learning. Ninety-six of the 328 neurons recorded in OFC and 60 of the 229 neurons recorded in ABL exhibited selective activity during evaluation of the odor cues after learning had occurred. A substantial proportion of those neurons in ABL developed selective activity very early in training, and many reversed selectivity rapidly after reversal. In contrast, those neurons in OFC rarely exhibited selective activity during odor evaluation before the rats reached the criterion for learning, and far fewer reversed selectivity after reversal. The findings support a model in which ABL encodes the motivational significance of cues and OFC uses this information in the selection and execution of an appropriate behavioral strategy.

Action Potentials↗

PubMedDate not supplied

Forgetting numbers in old age: strategy and learning speed matter.

BACKGROUND: Memory intervention research with older adults has primarily focused on immediate effects of training. Little is known about whether memory training can prevent forgetting of a learned material over time. OBJECTIVE: The main purpose of this study was to investigate the effects of memory training on forgetting of numerical information in old age. In addition, the effect of speed of learning on forgetting rate was examined. METHODS: Two training programs were employed contrasting a number-consonant mnemonic strategy with a self-generated strategy. A non-practice control group was also included. There were 20 participants in each group (age range=60-83 years). Following completion of training, participants memorized six 4-digit numbers to perfection. Retention was tested after 30 min, 24 h, 7 weeks, and 8 months. RESULTS: The three groups showed equal rates of forgetting across the first two follow-up assessments. A different picture emerged for the last two occasions, with the self-generated strategy group remembering more items relative to the two other groups. Moreover, participants reaching the criterion in few trials exhibited less forgetting than slow learners. CONCLUSIONS: These data indicate that self-generated strategy training may have advantages over learning a classical mnemonic for preventing long-term forgetting of numeric materials in old age.

Aged↗

PubMed2005

Cortical activation during Pavlovian fear conditioning depends on heart rate response patterns: an MEG study.

In the present study, we examined stimulus-driven neuromagnetic activity in a delayed Pavlovian aversive conditioning paradigm using steady state visual evoked fields (SSVEF). Subjects showing an accelerative heart rate (HR) component to the CS+ during learning trials exhibited an increased activation in sensory and parietal cortex due to CS+ depiction in the extinction block. This was accompanied by a selective orientation response (OR) to the CS+ during extinction as indexed by HR deceleration. However, they did not show any differential cortical activation patterns during acquisition. In contrast, subjects not showing an accelerative HR component but rather unspecific HR changes during learning were characterized by greater activity in left orbito-frontal brain regions in the acquisition block but did not show differential SSVEF patterns during extinction. The results suggest that participants expressing different HR responses also differ in their stimulus-driven neuromagnetic response pattern to an aversively conditioned stimulus.

Adult↗

PubMed1998

Effects of the serotonin agonists 8-OH-DPAT, buspirone, and DOI on water maze performance.

We have previously reported that the serotonin 5-HT1A agonist 8-OH-DPAT and the 5-HT2c agonist TFMPP impair performance on a water maze. In the present report we extended those studies by examining a second 5-HT1A agonist, buspirone, to see whether its effects paralleled those of 8-OH-DPAT, and by testing the effects of the 5-HT2 agonist DOI. Unlike the open pool Morris water maze, the maze used in these experiments has alleys and doorways. The maze can be easily reconfigured to present rats with both previously learned or new maze challenges. Performance is assessed by time to reach the maze exit platform and the number of wrong doorways entered (errors). At doses that did not affect performance in a previously learned maze, the 5-HT1A agonists 8-OH-DPAT (0.1 mg/kg) and buspirone (1 mg/kg) slowed acquisition of a new maze configuration as measured by both swim time to the exit platform and errors committed. A higher dose of buspirone (10 mg/kg) completely blocked acquisition of a novel maze. In contrast. DOI slowed performance as assessed by swim time on both a well-learned maze as well as acquisition of a new maze, but did not affect error rate on either task, suggesting that this 5-HT2 agonist impaired performance by depressing motor activity. These experiments demonstrate that serotonin agonists, especially the 5-HT1A subtype, can impair learning.

8-Hydroxy-2-(di-n-propylamino)tetralin↗