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Articles 181 - 194 of 194

Full-Text Articles in Psychology

Behavioral Stress Modifies Hippocampal Plasticity Through N-Methyl-D-Aspartate Receptor Activation, Michael R. Foy Jan 1996

Behavioral Stress Modifies Hippocampal Plasticity Through N-Methyl-D-Aspartate Receptor Activation, Michael R. Foy

Michael R. Foy

Behavioral stress has detrimental effects on subsequent cognitive performance in many species, including humans. For example, humans exposed to stressful situations typically exhibit marked deficits in various learning and memory tasks. However, the underlying neural mechanisms by which stress exerts its effects on learning and memory are unknown. We now report that in adult male rats, stress (i.e., restraint plus tailshock) impairs long-term potentiation (LTP) but enhances long-term depression (LTD) in the CA1 area of the hippocampus, a structure implicated in learning and memory processes. These effects on LTP and LTD are prevented when the animals were given CGP39551 (the …

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Hemispheric Differences Are Found In The Identification, But Not The Detection, Of Low Versus High Spatial Frequencies, Joseph B. Hellige Jan 1990

Hemispheric Differences Are Found In The Identification, But Not The Detection, Of Low Versus High Spatial Frequencies, Joseph B. Hellige

Psychological Science Faculty Works

The processing of sine-wave gratings presented to the left and right visual fields was examined in four experiments. Subjects were required either to detect the presence of a grating (Experiments 1 and 2) or to identify the spatial frequency of a grating (Experiments 3 and 4). Orthogonally to this, the stimuli were presented either at threshold levels of contrast (Experiments 1 and 3) or at suprathreshold levels (Experiments 2 and 4). Visual field and spatial frequency interacted when the task required identification of spatial frequency, but not when it required only stimulus detection. Regardless of contrast level (threshold, suprathreshold), high-frequency …

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Erratum: Hemispheric Differences Are Found In The Identification, But Not The Detection, Of Low Versus High Spatial Frequencies, Joseph B. Hellige Jan 1990

Erratum: Hemispheric Differences Are Found In The Identification, But Not The Detection, Of Low Versus High Spatial Frequencies, Joseph B. Hellige

Psychological Science Faculty Works

No abstract provided.

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Visual Laterality For Letter Comparison: Effects Of Stimulus Factors, Response Factors, And Metacontrol, Joseph B. Hellige Jan 1989

Visual Laterality For Letter Comparison: Effects Of Stimulus Factors, Response Factors, And Metacontrol, Joseph B. Hellige

Psychological Science Faculty Works

Right-handed subjects indicated whether two highly discriminable uppercase letters were the same or different. Letter pairs were projected to the left visual field/right hemisphere (LVF/RH) or the right visual field/left hemisphere (RVF/LH), or the same letter pair was presented to both visual fields simultaneously (bilateral trials). Laterality effects were not influenced by moderate blurring of the letters. However, on RVF/LH trials, reaction times were faster for same pairs than for different pairs. This effect was absent on LVF/RH trials, suggesting a qualitative difference in the mode of processing for the two unilateral trial types. The pattern of results on bilateral …

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Categorization Versus Distance: Hemispheric Differences For Processing Spatial Information, Joseph B. Hellige Jan 1989

Categorization Versus Distance: Hemispheric Differences For Processing Spatial Information, Joseph B. Hellige

Psychological Science Faculty Works

It has been hypothesized that the brain computes two different kinds of spatial-relation representations: one used to assign a spatial relation to a category and the other used to specify metric distance with precision. The present visual half-field experiment offers support for this distinction by showing that the left and right cerebral hemispheres make more effective use of the categorization and metric distance representations, respectively. Furthermore, the inclusion of a bilateral stimulus presentation condition permits the computation of a reversed association that offers additional support for the distinction between two types of spatial-relation representation.

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Effects Of Retinal Size On Visual Laterality, Joseph B. Hellige Jan 1987

Effects Of Retinal Size On Visual Laterality, Joseph B. Hellige

Psychological Science Faculty Works

Observers indicated whether two vertically presented bars were aligned one above the other (same trials) or were offset by an amount equal to the width of the bars on that trial (different trials). Retinal size was varied by using bars of three different widths (wide, medium, narrow). On different trials, reaction time to make correct responses was longer for narrow stimuli than for the other two sizes; this size effect was larger when stimuli were projected to the right visual field than when stimuli were projected to the left visual field. Such effects were not found on same trials. Implications …

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Effects Of Stimulus Duration On Processing Lateralized Faces, Joseph B. Hellige Jan 1985

Effects Of Stimulus Duration On Processing Lateralized Faces, Joseph B. Hellige

Psychological Science Faculty Works

Observers indicated whether a single probe face presented to the left or right visual field was contained in a positive set of five male faces. In one task the distractor (i.e., negative) stimuli were also male faces, and in another task the distractor stimuli were female faces. For both tasks, reducing stimulus duration from 200 msec to 20 msec increased the percentage of errors, but for neither the percentage of errors nor the reaction time was there any stimulus duration × visual field interaction. In conjunction with earlier experiments using these same tasks, the results indicate that reducing stimulus duration …

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Case Effects In Letter-Name Matching: A Partial Replication, Joseph B. Hellige Jan 1984

Case Effects In Letter-Name Matching: A Partial Replication, Joseph B. Hellige

Psychological Science Faculty Works

When same-case letter pairs are to be physically matched as “same” or “different,” reaction times (RTs) are generally shorter for “same” responses. The advantage in RT increases when such pairs are intermixed in blocks of trials also containing mixed-case pairs to be matched for name identity. These results have been interpreted as supportive of a two-code hypothesis of letter matching: In pure blocks of same-case pairs, a visual or physical code underlies letter matching, whereas in intermixed blocks, a phonetic or name code must be used for all “different” judgments. The theory predicts, however, that there should be little discrepancy …

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Case Effects In Letter-Name Matching: A Qualitative Visual Field Difference, Joseph B. Hellige Jan 1981

Case Effects In Letter-Name Matching: A Qualitative Visual Field Difference, Joseph B. Hellige

Psychological Science Faculty Works

Subjects indicated whether or not two letters presented simultaneously to the left or right visual field had the same name. On same-name trials, reaction time was faster when both letters had the same case (physically identical, or PI, pairs) than when they were of different case (name identical, or NI, pairs) and reaction time was faster for left visual field presentations than for right visual field presentations. For left visual field presentations, the letter-case effect was as large on different-name trials as on same-name trials, indicating that the NI-PI difference was not simply a physical identity effect. In contrast, for …

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Influence Of Noun Imagery On Speed Of Naming Nouns, Joseph B. Hellige Jan 1977

Influence Of Noun Imagery On Speed Of Naming Nouns, Joseph B. Hellige

Psychological Science Faculty Works

In an experiment on the influence of noun imagery on the speed of naming visually presented nouns, it was found that high-imagery nouns were named, on an average, 14 msec faster than low-imagery nouns. The difference, although small, was highly significant [F(l,14) = 10.04]. The magnitude of this effect was about one-third of that obtained when subjects were required to identify the grammaticality of phrases containing these same nouns, indicating that speed of encoding was probably a more important factor than speed of recognition in producing a noun imagery effect in speed of grammaticality judgments.

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The Importance Of Figural Relationships Between Target And Mask, Joseph B. Hellige Jan 1977

The Importance Of Figural Relationships Between Target And Mask, Joseph B. Hellige

Psychological Science Faculty Works

No abstract provided.

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The Role Of Noun Imagery In The Speed Of Processing The Grammaticality Of Adjective-Noun Phrases, Joseph B. Hellige Jan 1977

The Role Of Noun Imagery In The Speed Of Processing The Grammaticality Of Adjective-Noun Phrases, Joseph B. Hellige

Psychological Science Faculty Works

This experiment investigated speed of processing the grammaticality of phrases consisting of the adjective "one" or "two" followed by a singular or plural noun. The subject's task was to press one of two keys, depending upon whether the phrase was grammatically correct or incorrect. There were eight types of phrases, formed by the factorial combinations of singular or plural adjectives, singular or plural nouns, and high or low noun imagery. These served as within-subjects variables. Between-subjects variables were the factorial combinations of sex of subject, duration of stimulus phrase (.2 or 2.5 sec), and hand assigned to the correct-grammar key. …

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Finite Integer Analysis Of Individual Subject Protocols During Eyelid Conditioning, Joseph B. Hellige Jan 1976

Finite Integer Analysis Of Individual Subject Protocols During Eyelid Conditioning, Joseph B. Hellige

Psychological Science Faculty Works

Theios (1972) has proposed that during classical eyelid conditioning the conditioned response protocols of “voluntary” responders (Vs) will require an additional stage, relative to “conditioned” responders (Cs), to be adequately described. In a test of this hypothesis, individual subject protocols from eyelid conditioning experiments using both classical and avoidance modes of reinforcement were subjected to finite integer analysis (Theios, 1968). During both modes of reinforcement, a two-state Markov model was found to provide an adequate description of most individual protocols for both Cs and Vs. In addition, there were no indications that Vs give predominantly C-form conditioned responses at the …

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Changes In Same-Different Laterality Patterns As A Function Of Practice And Stimulus Quality, Joseph B. Hellige Jan 1976

Changes In Same-Different Laterality Patterns As A Function Of Practice And Stimulus Quality, Joseph B. Hellige

Psychological Science Faculty Works

Accuracy and reaction time (RT) of judgments about sameness vs. difference of (a) names of two letters and (b) shapes of two nonverbal forms were examined for stimuli presented to the center, left (LVF), and right (RVF) visual fields. For same-name letter pairs during Experiment I, responses were more accurate and faster for LVF than for RVF trials on an initial 90-trial block, but this difference was reversed by a third 90-trial block. The RVF advantage for RT was maintained over Trial Blocks 4 and 5, given during a second session, but had disappeared on Trial Blocks 6 through 9 …

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