How does the ecological foraging behavior of desert kangaroo rats (Dipodomys deserti) relate to their behavior on radial mazes?

Experiment 1 showed that laboratory-reared desert kangaroo rats, like domestic Norway rats, efficiently search for food on a radial arm maze (RAM) by avoiding revisiting arms within a trial. By placing an RAM on the floor so the animals could approach food from any direction, Experiment 2 tested whether efficient search by kangaroo rats was based on tactics of distance minimizing, central-place foraging, trail following, or meandering. In contrast to the dominant trail-following tactic of domestic Norway rats (Hoffman, Timberlake, Leffel, & Gont, 1999), kangaroo rats tended to distance minimize, whether maze arms were present or not. Experiment 3 indicated that kangaroo rats treated a floor configuration of eight food cups as two patches of four, based on beeline travel between patches and meandering within them. We conclude that similar performance in an elevated RAM by different species can be based on different tactics, and we suggest that a laboratory apparatus can be used to cast light on niche-related mechanisms.     

Effects of right and left hemisphere damage on performance of the "Right Hemisphere Communication Battery"

A Hebrew adaptation of Gardner and Brownell's (1986) "Right Hemisphere Communication Battery" (HRHCB) was administered to 27 right brain-damaged (RBD) patients, 31 left brain-damaged (LBD) patients, and 21 age-matched normal controls. Both patient groups showed deficits relative to controls and overall there was no difference between the two patient groups. A factor analysis of patients' scores on the HRHCB yielded two interpretable factors, a verbal and a nonverbal one. These factors were not lateralized. Performance of patients on the HRHCB correlated significantly and positively with performance on most tests of basic language functions, measured with a Hebrew adaptation of the "Western Aphasia Battery" (HWAB) and with other cognitive functions measured with standardized neuropsychological tests. There were stronger correlations of HRHCB with subtests of the HWAB in LBD patients and with nonlanguage cognitive tests in RBD patients. In the LBD group, HRHCB subtests' scores correlated negatively with lesion extent in frontal and temporal perisylvian regions. Such localization was not observed in RBD patients. The results argue against selective right hemisphere (RH) involvement in the RHCB, alleged to measure pragmatic aspects of language use, and show, instead, bilateral involvement. The results also argue against a modular organization of these functions of language use, especially in the RH.     

Stem homographs and lemma level representations

Previous studies have found that priming a target like cerr-o ("hill") with an unmasked stem-homograph (e.g., cerr-ar, "to close") or with an unmasked allomorph of a stem-homograph (e.g., cierr-a, "he/she/it closes") has an inhibitory effect on target recognition. We report evidence from stem-homograph priming studies that implicate both morphological parsing and lexical selection processes at the lemma level. We argue that stem-homograph inhibition is the product of lexical selection mechanisms that are engaged just when a fully ambiguous stimulus (here, an inflectional stem) must be assigned one of its viable interpretations in order to afford conscious perception of lexical identity.     

College-educated women's personality development in adulthood: perceptions and age differences

Adulthood encompasses a large time span and includes a series of psychosocial challenges (E. H. Erikson, 1950). Five aspects of personality (identity certainty, confident power, concern with aging, generativity, and personal distress) were assessed in a cross-sectional study of college-educated women who at the time of data collection were young adults (age: M = 26 years), middle-aged adults (age: M = 46 years), or older adults (age: M = 66 years). Respondents rated each personality domain for how true it was of them at the time, and they then rated the other 2 ages either retrospectively or prospectively. Results are discussed with attention to the ways in which women's adult development may have been shaped by experiences particular to both gender and birth cohort, and to how these women fit with E. H. Erikson's theory of adult development.     

From agape to organs: religious difference between Japan and America in judging the ethics of transplant

This essay argues that Japan's resistance to the practice of transplanting organs from persons deemed "brain dead" may not be the result, as some claim, of that society's religions being not yet sufficiently expressive of love and altruism. The violence to the body necessary for the excision of transplantable organs seems to have been made acceptable to American Christians at a unique historical "window of opportunity" for acceptance of that new form of medical technology. Traditional reserve about corpse mutilation had weakened and, especially as presented by the theologian Joseph Fletcher, organ donation was touted as both expressive of agape and a way of "updating" Christianity via the ethics of Utilitarianism. Many Japanese, largely Buddhist and Confucian in their orientation, view these changed valorizations as neither necessary nor patently more ethical than those of their own traditions.     

Infants of depressed mothers,although competent learners,fail to learn in response to their own mothers' infant-directed speech

Depressed mothers use less of the exaggerated prosody that is typical of infant-directed (ID) speech than do nondepressed mothers. We investigated the consequences of this reduced perceptual salience in ID speech for infant learning. Infants of nondepressed mothers readily learned that their mothers' speech signaled a face, whereas infants of depressed mothers failed to learn that their mothers' speech signaled the face. Infants of depressed mothers did, however, show strong learning in response to speech produced by an unfamiliar nondepressed mother. These outcomes indicate that the reduced perceptual salience of depressed mothers' ID speech could lead to deficient learning in otherwise competent learners.     

From acquisition to consolidation: on the role of brain-derived neurotrophic factor signaling in hippocampal-dependent learning

One of the most rigorously investigated problems in modern neuroscience is to decipher the mechanisms by which experience-induced changes in the central nervous system are translated into behavioral acquisition, consolidation, retention, and subsequent recall of information. Brain-derived neurotrophic factor (BDNF) has recently emerged as one of the most potent molecular mediators of not only central synaptic plasticity, but also behavioral interactions between an organism and its environment. Recent experimental evidence indicates that BDNF modulates synaptic transmission and plasticity by acting across different spatial and temporal domains. BDNF signaling evokes both short- and long-term periods of enhanced synaptic physiology in both pre- and postsynaptic compartments of central synapses. Specifically, BDNF/TrkB signaling converges on the MAP kinase pathway to enhance excitatory synaptic transmission in vivo, as well as hippocampal-dependent learning in behaving animals. Emerging concepts of the intracellular signaling cascades involved in synaptic plasticity induced through environmental interactions resulting in behavioral learning further support the contention that BDNF/TrkB signaling plays a fundamental role in mediating enduring changes in central synaptic structure and function. Here we review recent literature showing the involvement of BDNF/TrkB signaling in hippocampal-dependent learning paradigms, as well as in the types of cellular plasticity proposed to underlie learning and memory.     

Neuropsychological testing for assessment of treatment effects: methodologic issues

Neuropsychological (NP) testing is now recognized as an important method for evaluating treatment effects. However, there are limitations to how these tests are currently used in most drug treatment protocols. Changes in cognition are typically defined in statistical terms, with little knowledge as to whether the observed differences are meaningful in any other sense. Methods for assessing changes in test scores need to account for test-retest reliability, practice effects, regression to the mean, and the impact of initial performance. All of these factors may vary according to the individual characteristics of the subject. This article reviews two methods from the NP literature that have attempted to account for these sources of test-retest bias. The reliable change index provides a confidence interval for predicted change by taking into account the test-retest reliability of the measure. Standardized regression-based measures use a more sophisticated statistical approach that enables them to better account for other potential sources of confound. Use of this methodology has been limited to studies of epilepsy surgery and sports-related concussion. These methods have the potential for enhancing the interpretation of NP test data in drug treatment protocols by providing an empirically based definition of clinically meaningful change.