Disengaging the negative priming mechanism in location tasks

In a location-based negative priming task, targets that appear at locations that were previously occupied by distractors are typically responded to more slowly than are targets that appear at formerly unoccupied positions. In the present study, we attempted to disengage the location-based negative priming mechanism by presenting visual cues indicating the most likely location of the upcoming target. The first experiment showed that 75% cue-target validity was not sufficient to affect the negative priming mechanism. However, the second experiment demonstrated that a much reduced, but not eliminated, negative priming effect occurred with 100%cue-target validity. These findings are similar to those found with inhibition of return, suggesting that location-based inhibition of return effects and location-based negative priming effects may share a common inhibition mechanism.     

The effects of imagery instructions on total congenital blind recall

Abstract

Research on the performance of total congenital blind subjects in imagery tasks is of particular interest because it helps to evaluate the consequences of their lack of visual experience. The present paper examines some points which remained unclear in the preceding research on the effects of imagery instructions on the recall of blind subjects. In Experiment 1 it is shown that, in a free recall task of unrelated nouns, the blind may take advantage of imagery instructions, independently of the particular requirement to form either common or bizarre images. In Experiment 2 the multiple image processing deficit of the blind found by De Beni and Cornoldi (1988) was again observed, but the effect was not found when the same quantity of material had to be processed verbally. Results are interpreted as showing that, although the blind may follow imagery instructions, their visual handicap creates specific difficulties in creating interactive images involving several items at the same time.     

A covariance structure analysis of employees' response to performance feedback

This longitudinal study used D. R. Ilgen, C. D. Fisher, and M. S. Taylor's (1979) feedback process model as a theoretical framework to determine whether a sequential chain of cognitive variables mediates an individual's response to performance feedback. One hundred two employees were surveyed 2 weeks after their performance appraisal, and performance was assessed 11 months later at the end of the review cycle. Covariance structure analysis supported the convergent and discriminant validity of the constructs underlying the model and the constellation of structural relationships. A set of cognitive variables was found to completely mediate the relationship between an individual's receipt and response to feedback. Implications for the feedback process and future research are discussed.     

Differential activity profile of cAMP-dependent protein kinase isoforms during long-term memory consolidation in the crab Chasmagnathus

The isoforms of cAMP-dependent protein kinase (PKA) show distinct biochemical properties and subcellular localization, suggesting different physiological functions, and conferring the fine-tuning between the activation of cAMP-PKA cascade and the cellular response. The critical role of PKA in memory and synaptic plasticity has been extensively demonstrated both in vertebrates and invertebrates, but the role of PKA isoforms is a matter of debate. Here we present experimental data showing differential PKA activation profiles after two different experiences: an instance of associative contextual learning (context-signal learning) and a single exposure to a novel context, both in the learning and memory model of the crab Chasmagnathus. Differences were found in the temporal course of activation and in the involvement of PKA isoforms. We found increased PKA activity immediately and 6 h after context-signal training correlating with the critical periods during which pharmacological inhibition of PKA disrupts memory formation. In contrast, PKA activity increased immediately but not 6 h after single exposure to a novel context. The amounts of PKA I and PKA II holoenzymes were analyzed to determine changes in holoenzyme levels and/or differential activation induced by both experiences. Results indicate that context-induced PKA activation is at least in part due to PKA II, and that PKA activation 6 h after context-signal learning coincides with an increase in the total level of PKA I. Considering the higher sensitivity of PKA I to cAMP, its increment can account for the PKA activation found 6 h after training and is proposed as a novel mechanism providing the prolonged PKA activation during memory consolidation.     

Animals' use of landmarks and metric information to reorient: effects of the size of the experimental space

Disoriented children could use geometric information in combination with landmark information to reorient themselves in large but not in small experimental spaces. We tested fish in the same task and found that they were able to conjoin geometric and non-geometric (landmark) information to reorient themselves in both the large and the small space used. Moreover, fish proved able to reorient immediately when dislocated from a large to a small experimental space and vice versa, suggesting that they encoded the relative rather than the absolute metrics of the environment. However, fish tended to make relatively more errors based on geometric information when transfer occurred from a small to a large space, and to make relatively more errors based on landmark information when transfer occurred from a large to a small space. The hypothesis is discussed that organisms are prepared to use only distant featural information as landmarks.     

Author Index Volume 7

Authors Index

Author Index Volume 7     

Selective Abolition of the NMDA Component of Long-Term Potentiation in Mice Lacking mGluR5

The mechanisms underlying the differential expression of long-term potentiation (LTP) by AMPA and NMDA receptors, are unknown, but could involve G-protein-linked metabotropic glutamate receptors. To investigate this hypothesis we created mutant mice that expressed no metabotropic glutamate receptor 5 (mGluR5), but showed normal development. In an earlier study of these mice we analyzed field-excitatory postsynaptic potential (fEPSPs) in CA1 region of the hippocampus and found a small decrease; possibly arising from changes in the NMDAR-mediated component of synaptic transmission. In the present study we used whole-cell patch clamp recordings of evoked excitatory postsynaptic currents (EPSCs) in CA1 pyramidal neurons to identify the AMPAR- and NMDAR-mediated components of LTP. Recordings from control mice following tetanus, or agonist application (IS, 3R-1-amino-cyclopentane 1,3-dicarboxylic acid) (ACPD), revealed equal enhancement of the AMPA and NMDA receptor-mediated components. In contrast, CA1 neurons from mGluR5-deficient mice showed a complete loss of the NMDA-receptor-mediated component of LTP (LTP_NMDA), but normal LTP of the AMPA-receptor-mediated component (LTP_AMPA). This selective loss of LTP_NMDA was seen in three different genotypic backgrounds and was apparent at all holding potentials (−70 mV to +20 mV). Furthermore, the LTP_NMDA deficit in mGluR5 mutant mice could be rescued by stimulating protein kinase C (PKC) with 4β-phorbol-12,13-dibutyrate (PDBu). These results suggest that PKC may couple the postsynaptic mGluR5 to the NMDA-receptor potentiation during LTP, and that this signaling mechanism is distinct from LTP_AMPA. Differential enhancement of AMPAR and NMDA receptors by mGluR5 also supports a postsynaptic locus for LTP.     

Needed: A Rededication to the Counselor's Primary Commitment

The counseling aspect of the counselor's role has been eroded recently by a number of negative influences. If this erosion is not halted the counselor will not have enough time to counsel because of an overinvolvement in noncounseling activities. Counselors must focus on and preserve counseling as their primary function if the counseling profession is to have a clear identity.