Changes in somatosensory evoked potentials and Hoffmann reflexes during fast isometric contraction of foot plantarflexor in humans

In the present study, the extent to which the early component of somatosensory evoked potentials (SEPs) and the Hoffmann (H-) reflex induced by stimulation of the posterior tibial nerve are altered during the ascending and descending phases of fast plantarflexion was investigated. SEPSs and H-reflex of the soleus following tibial nerve stimulation were examined during fast plantarfiexion when performed by nine normal subjects. The analyses focused on differences in amplitude modulation of the P30-P40 component of SEP and the H-reflex between the ascending and descending phases of full-wave rectified and averaged soleus electromyographic (EMG) activity. The H-reflex amplitude was significantly increased and decreased during the ascending and descending phases more than under resting control conditions, respectively. The reduction of SEP amplitude was 49% for the ascending phase and 83% for the descending phases with respect to the resting situation. Modulation of SEP during the ascending and descending phases was robustly retained even during ischemic nerve blockade of large diameter afferent fibers. These findings suggest that the transmission of afferent inputs from muscle spindles to motoneurons and to the somatosensory cortex during fast isometric contraction of the plantar flexor is regulated in a time-dependent fashion by descending commands.     

When knowing more means less: the effect of fan on metamemory judgments

The authors used a "fan" paradigm (J. R. Anderson, 1974) to test the accessibility and competition models of metamemory using judgments of learning (JOLs). JOLs in this study reflect one's confidence level in subsequently recognizing newly learned material. The number of facts, or "fan," associated with JOL-queried concepts varied from 1 to 3 associates. Results of 3 experiments indicated that as the level of fan increased, the magnitude of JOLs decreased. This finding was observed even when the fan effect (i.e., slower recognition as number of facts increase) was attenuated on a verification task in 2 of the experiments by manipulating the organization of the multiple concepts. The results supported the competition hypothesis (T. A. Schreiber, 1998; T. A. Schreiber & D. L. Nelson, 1998) as an important determinant of JOLs.     

Left-side dominance for song discrimination in Bengalese finches (Lonchura striata var. domestica)

Male Bengalese finches are left-side dominant for the motor control of song in the sensorimotor nucleus (the high vocal center, or HVc) of the telencephalon. We examined whether perceptual discrimination of songs might also be lateralized in this species. Twelve male Bengalese finches were trained by operant conditioning to discriminate between a Bengalese finch song and a zebra finch song. Before training, the left HVc was lesioned in four birds and the right HVc was lesioned in four other birds. The remaining four birds were used as controls without surgery. Birds with a left HVc lesion required significantly more time to learn to discriminate between the two songs than did birds with a right HVc lesion or intact control birds. These results suggest that the left HVc is not only dominant for the motor control of song, but also for the perceptual discrimination of song. Accepted after revision: 11 September 2001 Electronic Publication     

Contextual learning induces an increase in the number of hippocampal CA1 neurons expressing high levels of BDNF

We examined behaviorally induced expression of brain-derived neurotrophic factor (BDNF) in area CA1 of the hippocampus. Sprague-Dawley rats were trained in a contextual fear conditioning (CFC) task, sacrificed 4h later, and their brains were processed for immunohistochemistry. We found distinctively high levels of BDNF immunoreactivity in a small number ( approximately 1%) of CA1 neurons in untrained animals. The number of these exceptional neurons, which are identified as BDNF(++) in this study, was increased by up to approximately 3% after CFC. This increase was blocked in the presence of a memory-impairing dose of a NMDA receptor antagonist (MK801 0.3 mg/kg, i.p.) given 30 min prior to training. The BDNF signal intensity in BDNF(++) neurons correlated with that of surrounding glutamic acid decarboxylase (GAD) 65. This correlation between GAD65 and BDNF signal intensities suggests that BDNF upregulation was associated with increased signaling via inhibitory GABAergic synapses that would lessen further intervening neuronal activity. Our observation that neurons which upregulate BDNF expression following a learning experience are rich in GAD65-enriched afferent synapses suggests that these neurons may have distinct roles in memory consolidation.     

Cultural differences related to positive and negative valence

Differences between North American and East Asian cultures were examined in terms of the valence of psychological constructs. Americans were more likely than Japanese to focus on positive things. In contrast, Japanese ( vs Americans) were more likely to attend to negative information of the self, but not more or less likely to focus on negative things about others. Based on within-culture analyses, the Americans' data were better described by their tendency to focus on positive things over negative things than by their tendency for self-enhancement. In contrast, the Japanese data were better described by their self-critical tendency. This result was replicated in a second study. In addition, correlations between constructs with opposite valences were negative in the USA, but positive or absent in Japan.     

Judgments of associative memory

Judgments of associative memory (JAM) were indexed by ratings given to pairs of cue and response words. The normed probabilities, p(response|cue), were obtained from free association norms. The ratings were linearly related to the probabilities. The JAM functions were characterized by high intercepts ( approximately 50 on a 100 point scale) and shallow slopes (<0.5). The JAM function generalized across materials and method of rating. The function was not affected by expectancies or semantic similarity. Attempts to alter the function by making alternative responses more available were unsuccessful. A computer simulation model (MINERVA 2) exhibited the linear JAM function and successfully accounted for more complex phenomena (like the joint influence of forward and backward associative strengths on ratings). The shallow JAM slope appears to result from a fundamental lack of discrimination among associative strengths. The high intercept appears to result partly from an independent post-mnemonic source of bias producing over-estimation of association.     

Intervening with Multiplication Fact Difficulties: Examining the Utility of the Instructional Hierarchy to Target Interventions

Examining the use of conceptual frameworks such as the instructional hierarchy (IH) to drive academic interventions represents an important area of inquiry in order to understand why an intervention was effective. However, to date, the IH has only been examined retroactively to explain the effectiveness of math interventions and has not been used to drive intervention implementation based on students’ needs. Therefore, the current study used a multiple baseline single-case design to examine the utility of the IH to determine an appropriately targeted acquisition (incremental rehearsal) or proficiency (timed drill) intervention for difficulties with multiplication facts. Students first received the contraindicated intervention (i.e., non-targeted) and then their correctly targeted intervention. Results showed that all students demonstrated greater fluency growth during their targeted intervention and that students in need of an acquisition intervention also demonstrated greater multiplication fact retention and growth rate during their targeted intervention. The utility of the IH as a heuristic to correctly target interventions based on students’ baseline skill levels is discussed.

     

Keeping an “I” on PRIDE: Measuring Imitation in Parent-Child Interaction Therapy

In parent–child interaction therapy (PCIT), therapists encourage parents to imitate child behaviors in order to convey approval of the child’s actions and promote the development of linguistic and social–cognitive skills. However, the Dyadic Parent-Child Interaction Coding System (DPICS-IV), used to measure skills taught during PCIT, does not include guidelines for coding parent–child imitation, making it difficult to determine how PCIT affects it. The current study addresses this problem by developing guidelines for coding imitation, which were then used to code DPICS-IV segments from 58 Mexican American families that participated in a past clinical trial. Results suggest that these coding guidelines can be used to reliably measure parent and child imitation. A series of additional analyses supported the construct validity of the codes. Specifically, there was a trend for parent imitation, but not child imitation, to increase more from pre–post treatment in PCIT relative to treatment as usual. In addition, parents who imitate their children were found to have children who imitate them more in return. Finally, improvement in parent imitation, but not child imitation, was significantly related to a decrease in child behavior problems. Further study is needed to determine the optimal frequency of imitation, and findings suggest that additional attention to coaching imitation may be warranted.     

A Study of the Conceptual Structure of Growth Mindsets and Their Impact on Self-Improvement Motivation

This study examined the conceptual structure and motivational effects of growth mindsets based on the perspective of character strengths. An internet survey was conducted with 1,000 workers (500 males and 500 females; age range 20–59 years, M = 40.1 years, SD = 10.7 years). Participants were presented with 25 strengths (i.e., intelligence and 24 character strengths) and were asked to rate their perceived competence, growth mindset, and improvement intention for each strength. The exploratory factor analyses on perceived competence, growth mindset, and improvement intention identified five common factors: wisdom, willpower, temperance, transcendence, and groupness. Moreover, regression analyses indicated that a growth mindset was more strongly related to improvement intention than perceived competence. Furthermore, regression analyses found domain-specific effects of growth mindsets on improvement intention. Thus, the intention to improve a particular strength was more closely related to that particular growth mindset than to other growth mindsets. The theoretical and educational implications are aired in the discussion section.