PubMed Health⌕ Search

Biomedical subjects

Thomas Jacobsen

Publications and source records attributed to Thomas Jacobsen.

7 recordsLinked to original sources
PubMed2003

Mismatch negativity to pitch change: varied stimulus proportions in controlling effects of neural refractoriness on human auditory event-related brain potentials.

Based on a memory-comparison process, changes in the pitch of repetitive sounds are pre-attentively detected, reflected by the mismatch negativity (MMN) event-related brain potential (ERP). In such oddball sequences, ERP responses are also affected by differential refractory states of frequency-specific afferent cortical neurons. This contamination of MMN can be controlled using an additional blocked sequence of equiprobable tones. The present study investigated effects of varying the in-sequence probabilities of these control tones from 10 to 45%, respectively. Results showed that an equal distribution of all control-sequence tones is not necessary for efficiently removing neural refractoriness effects on the ERPs. The genuine memory-comparison-based frequency-change MMN can be estimated using sequences, within which the number of equiprobable control tones varies between three and nine.

Adult↗
PubMed2003

Measuring duration mismatch negativity.

OBJECTIVE: Automatic comparisons of sound duration in auditory sensory memory are typically investigated by comparing event-related potentials (ERPs) to standard and deviant stimuli presented in oddball blocks. Deviants elicit mismatch negativity (MMN). This procedure might overestimate an MMN contribution reflecting automatic sensory memory processes because of differential states of refractoriness of respectively recruited neural populations [Neuroreport 1996;7:3005; Psychophysiology 2001;38:723]. Here, memory-comparison-based Duration MMN contributions were investigated using various experimental protocols. METHODS: Memory-comparison-based first-order Duration MMN was investigated using 4 blocked conditions: (a) descending Deviant (100 ms, P=0.14), 150 ms Standard; (b) reverse ascending Deviant (150 ms), 100 ms Standard; (c) Control comprised of 7 equiprobable durations between 25 and 175 ms; and additionally (d) equiprobable tones between 100 and 400 ms. Using the former 3 conditions, Deviants, Standards and Controls were physically identical. RESULTS: Comparing Deviants and Controls excluded potential refractoriness effects, and a decomposition of memory-comparison-based MMN and residual MMN was demonstrated. Genuine Duration MMN was also obtained in the deviant-standard-reverse comparison. CONCLUSIONS: Using a blocked control condition yielded equivalent results to reversing the role of deviant and standard in two separate oddball blocks. Using the reverse ascending deviant condition is thus sufficient as a control.

Acoustic Stimulation↗
PubMed2003

Timed picture naming in seven languages.

Timed picture naming was compared in seven languages that vary along dimensions known to affect lexical access. Analyses over items focused on factors that determine cross-language universals and cross-language disparities. With regard to universals, number of alternative names had large effects on reaction time within and across languages after target-name agreement was controlled, suggesting inhibitory effects from lexical competitors. For all the languages, word frequency and goodness of depiction had large effects, but objective picture complexity did not. Effects of word structure variables (length, syllable structure, compounding, and initial frication) varied markedly over languages. Strong cross-language correlations were found in naming latencies, frequency, and length. Other-language frequency effects were observed (e.g., Chinese frequencies predicting Spanish reaction times) even after within-language effects were controlled (e.g., Spanish frequencies predicting Spanish reaction times). These surprising cross-language correlations challenge widely held assumptions about the lexical locus of length and frequency effects, suggesting instead that they may (at least in part) reflect familiarity and accessibility at a conceptual level that is shared over languages.

Cross-Cultural Comparison↗
PubMed2002

Visual marking for search: behavioral and event-related potential analyses.

Visual marking is an attentional mechanism of prioritizing the selection of new static or moving objects via top-down intentional inhibition of old objects [Psychol. Rev. 104 (1997) 90-122]. The present study investigated the operation of visual marking using event-related brain potentials (ERPs). Participants searched a display for one of two target letters among randomly selected letter distractors. Two item set sizes were used in a two-stage display. Half of the items appeared for 1000 ms in the first stage followed by the remainder in the second stage. Three blocked conditions were used. In the Preview condition, targets appeared as one of a set of new items in Display 2. Items in Display 1 could thus be excluded from search by visual marking. In the Control condition, old items changed when new items appeared, and the target was equally likely to be at an old or a new position. In this condition marking is unlikely to be engaged since old locations could contain the target. In the Search condition, targets appeared either in Display 1 (80%) or Display 2 (20%), and Display 1 items did not change. The results showed condition-contingent attentional modulations in the N1/N2 range. In addition, a broadly distributed centrally-preponderant sustained negativity was obtained in the 350-750 ms time range after the onset of Display 1 for the Preview-Control comparison. This latter negativity is interpreted to reflect the processes involved in setting up and maintaining of visual marking. It demonstrated an effect of visual marking well prior to Display 2 onset, thereby ruling out an account of the preview benefit solely due to attentional capture by Display 2 item onset.

Adult↗
PubMed2002

Aesthetic judgments of novel graphic patterns: analyses of individual judgments.

Aesthetic judgments were investigated using a combined nomothetic and idiographic approach. Participants judged novel graphic patterns with respect to their own personal definitions of "beauty." Judgment analysis was employed to derive individual case models of judgment strategies as well as a group model. As predicted, symmetry had the highest correlations with aesthetic judgments of beauty. Stimulus complexity was the second-highest correlate of a positive evaluation. Thus, there was agreement at the group level. The judgment analyses, however, indicated substantial individual differences. These included use of symmetry or complexity cues that were contrary to the main group use, e.g., a few participants considered nonsymmetric patterns more beautiful. These findings suggest that exclusive consideration of the group model would have leveled the individual differences and been misleading. The group model is significant; however, the individual judgment analyses represent individual patterns of judgment in a notedly more accurate way.

Adult↗
PubMed2002

Kandinsky's questionnaire revisited: fundamental correspondence of basic colors and forms?

Kandinsky postulated a fundamental correspondence between color and form. Using a variant of his historical questionnaire, 200 (92 men, 108 women) nonartist university students were divided into two groups and asked to assign the colors yellow, red, and blue to the triangle, square, and circle in a one-to-one fashion. One group worked under a mere color-form correspondence instruction, the other under an aesthetic-correspondence one, i.e., this latter group was asked to make the most beautiful color-form assignment. Participants' assignments showed a clear, stable group preference. About half of the students assigned red to the triangle, blue to the square, and yellow to the circle, respectively. This preferred assignment stood regardless of variation in instruction. Frequently, world knowledge associations were stated in the rationale for an assignment choice. The red triangle resembled a traffic sign, a warning triangle, and the yellow circle resembled the sun. Kandinsky's assignment, however, was the least preferred one. It is argued that color-form assignments as well as the motivation to produce them are due to a multitude of factors. World knowledge, education, historical change, societal, group-specific, and individual leitmotifs are all influences.

Adolescent↗