Biomedical subjects

Chad J Marsolek

Publications and source records attributed to Chad J Marsolek.

9 recordsLinked to original sources

PubMed2005

Does a causal relation exist between the functional hemispheric asymmetries of visual processing subsystems?

Past research indicates that specific shape recognition and spatial-relations encoding rely on subsystems that exhibit right-hemisphere advantages, whereas abstract shape recognition and spatial-relations encoding rely on subsystems that exhibit left-hemisphere advantages. Given these apparent regularities, we tested whether asymmetries in shape processing are causally related to asymmetries in spatial-relations processing. We examined performance in four tasks using the same stimuli with divided-visual-field presentations. Importantly, the asymmetry observed in any one task did not correlate with the asymmetries observed in the other tasks in ways predicted by extant theories. Asymmetries in shape processing and spatial-relations encoding may not be due to a common causal force influencing multiple subsystems.

Adult↗

PubMed2005

Initial storage of unfamiliar objects: examining memory stores with signal detection analyses.

The memory source(s) underlying performance of the object decision task were examined. Application of signal detection theory with independent indices of sensitivity and bias indicated that greater object decision sensitivity (possible vs. impossible object discrimination) is observed for primed than for unprimed objects and a greater bias to respond "possible" is observed for primed than for unprimed objects. To test whether a single memory store underlies the two effects, we assessed whether the two effects would be influenced in similar ways by a particular experimental manipulation. Sensitivity did not differ between processing of 180 degrees -rotated primed objects vs. un-rotated primed objects, but bias to respond "possible" differed between those conditions in predictable ways depending on the cerebral hemisphere of direct test presentations. Results support a conciliatory resolution to the debate concerning memory in this task and help to clarify properties of memory stores underlying the initial storage of unfamiliar objects.

Adult↗

PubMed2005

A critical boundary to the left-hemisphere advantage in visual-word processing.

Two experiments explored boundary conditions for the ubiquitous left-hemisphere advantage in visual-word recognition. Subjects perceptually identified words presented directly to the left or right hemisphere. Strong left-hemisphere advantages were observed for UPPERCASE and lowercase words. However, only a weak effect was observed for AlTeRnAtInG-cAsE words, and a numerical reversal of the typical left-hemisphere advantage was observed for words in a visual prototype font (a very unfamiliar word format). Results support the theory that dissociable abstract and specific neural subsystems underlie visual-form recognition and fail to support the theory that a visual lexicon operates in the left hemisphere.

Attention↗

PubMed2005

Evidence for dissociable neural mechanisms underlying inference generation in familiar and less-familiar scenarios.

In this study, we investigated whether the left and right hemispheres are differentially involved in causal inference generation. Participants read short inference-promoting texts that described either familiar or less-familiar scenarios. After each text, they performed a lexical decision on a letter string (which sometimes constituted an inference-related word) presented directly to the left or right hemisphere. Response-time results indicated that hemisphere of direct presentation interacted with type of inference scenario. When test stimuli were presented directly to the left hemisphere, lexical decisions were facilitated following familiar but not following less-familiar inference scenarios, whereas when test stimuli were presented directly to the right hemisphere, facilitation was observed in both familiar and less-familiar conditions. Thus, inferences may be generated in different ways depending on which of two dissociable neural subsystems underlies the activation of background information.

Adult↗

PubMed2005

Interactive visual and postvisual processes and their roles in form-specific memory.

Effects of depth of encoding on form-specific memory were examined. After viewing words (e.g., "bear") presented centrally during initial encoding, participants completed word stems (e.g., "BEA") presented laterally and pattern masked during subsequent test. When the encoding task was perceptual, letter-case specific memory was not observed, unlike in previous experiments without pattern masking. However, when the encoding task required both perceptual and conceptual processing, letter-case specific memory was observed in direct right-hemisphere, but not in direct left-hemisphere, test presentations, like in previous studies without pattern masking. Results were not influenced by whether stems were completed to form the first words that came to mind or words explicitly retrieved from encoding. Depth of encoding may influence form-specific memory through interactive processing of visual and postvisual information.

Concept Formation↗

PubMed2003

Sensitivity reductions in false recognition: a measure of false memories with stronger theoretical implications.

Signal detection analyses of recognition memory indicate that a bias to respond "old" is large for critical words that are centrally related with previously encoded word lists, is small for words that are less related, and is not observed for unrelated words. Also, recognition sensitivity has not been previously shown to differ between those conditions, which has focused debate over how to explain false recognition on the bias differences. In 3 experiments, critical-word sensitivity was lower than sensitivity for other word types, but related-word sensitivity was not lower than sensitivity for unrelated words. Extant models that predict reduced critical-word sensitivity also predict lower sensitivity for related words than for unrelated words. These results provide crucial new constraints on theoretical explanations of false memories.

Attention↗

PubMed2003

Serotonin levels influence patterns of repetition priming.

Repetition priming in a word-stem completion task was examined in a group of control subjects and in a group of experimental subjects under conditions of acute tryptophan depletion (T-) and tryptophan augmentation (T+). Experimental subjects ingested amino acid compounds that depleted or loaded the body with tryptophan, and word-stem completion priming performance was measured. Results indicate differential effects of T- and T+ manipulations on word-stem completion priming. In the control group, both specific-visual and amodal priming were observed. Conversely, in the T+ condition, specific-visual priming, but no amodal priming, was observed, whereas in the T- condition, amodal priming, but no specific-visual priming, was observed. The authors conclude that serotonin (5-hydroxytryptamine) plays a critical role in repetition priming by helping to modulate which neural systems contribute to priming effects.

Adolescent↗

PubMed2002

Interhemispheric communication of abstract and specific visual-form information.

Pairs of letters were compared after being viewed in different visual fields (i.e. across-hemispheres, AH) or in the same visual field (i.e. within-hemisphere, WH). In an abstract-category comparison task, participants decided whether two letter exemplars belonged to the same abstract category (e.g. "k" and "K") or not (e.g. "k" and "P") and performed more accurately in AH trials than in WH trials. In a specific-exemplar comparison task, they decided whether two letters within the same abstract category were the same specific exemplars (e.g. "k" and "k") or not (e.g. "k" and "K") and performed more accurately in WH trials than in AH trials. This pattern of results was observed when the exemplars in a category were visually similar (e.g. "k" and "K", "a" and "a") but not when they were visually dissimilar (e.g. "a" and "A"). The reversed association technique was used to confirm the independence of subsystems underlying abstract category and specific-exemplar comparisons. Most important, the results support the theory that a specific-exemplar subsystem is more detrimentally affected by interhemispheric transfer of information than an abstract category subsystem.

Adult↗

PubMedDate not supplied

Hemispheric asymmetries in memory processes as measured in a false recognition paradigm.

Although memory differs in important ways between the left and right cerebral hemispheres, the nature of these differences remains controversial. We examined this issue in two experiments using a false memory paradigm that allowed novel tests of two theories that have not been assessed in a common paradigm previously. Lists of semantically related words (e.g., bed, rest, wake...), all highly associated to one "critical" word (e.g., sleep), were presented auditorily during a study phase. Memory for both the related words and the critical words was measured in a subsequent old/new recognition test using divided-visual-field word presentations. The most important results were that the ability to correctly reject previously unpresented words was greater when test items were presented to the right visual field/left hemisphere (RVF/LH) than to the left visual field/right hemisphere (LVF/RH) and that participants were more confident in correctly rejecting unpresented words when test items were presented to the RVF/LH than to the LVF/RH. Results were in line with the theory that associative activation of semantic information is restricted in the left hemisphere but diffuse in the right; however, these results contrasted with the theory that memory traces are interpretive in the left hemisphere but veridical in the right. A potential resolution to the seemingly contradictory theories of asymmetries in memory processing is briefly discussed.

Acoustic Stimulation↗