Suppression of EEG gamma activity may cause the attentional blink

The attentional blink (AB) is an impairment of attention, which occurs when subjects have to report a target stimulus (T2) following a previous target (T1) with a short delay (up to 600 ms). Theories explaining the AB assume that processing of T2 is more vulnerable to decay or substitution, as long as attention is allocated to T1. Existing models of the AB, however, do not account for the fact that T2 detection accuracy reaches the minimum when T2 is presented after about 300 ms and not immediately following T1. Therefore, a new model is suggested, which is based on chronometrical considerations together with recent neurophysiological findings concerning the relation between the P3 event-related potential and the AB, the interaction between P3 and gamma oscillations, and the significance of the early evoked gamma band response. We hypothesize that suppression of the early gamma response to T2, accompanying the P3 related to T1, causes the AB.     

Dichotic listening and sleep deprivation: vigilance effects

Twelve sleep-deprived and 13 non-deprived Navy cadets were tested with the dichotic listening procedure for effects of sleep deprivation on hemispheric asymmetry and sustained attention. Consonant-vowel syllables were presented to the subjects in three different conditions, a divided (non-forced) attention condition, a forced right ear and a forced left ear attention condition. In the two forced attention conditions the subjects were instructed to focus attention only on the right or left ear stimulus. The results showed an expected right ear advantage for both groups during the non-forced and forced right attention conditions, indicating superior left hemisphere processing. During the forced left attention condition, the sleep-deprived subjects showed no ear advantage at all, while the non-deprived subjects showed an expected left ear advantage. The results are discussed within a theoretical framework of a dual process model, where sleep deprivation disrupts the ability to sustain attention, caused by a temporary failure of the right hemisphere's top-down (instruction-driven) processing to override the left hemisphere's bottom-up (stimulus-driven) processing.     

Prioritization in visual search: visual marking is not dependent on a mnemonic search

Visual marking (VM) refers to our ability to completely exclude old items from search when new stimuli are presented in our visual field. We examined whether this ability reflects an attentional scan of the old items, possibly allowing observers to apply inhibition of return or maintain a memory representation of already seen locations. In four experiments, we compared performance in two search conditions. In the double-search (DS) condition, we required participants to pay attention to a first set of items by having them search for a target within the set. Subsequently, they had to search a second set while the old items remained in the field. In the VM condition, the participants expected the target only to be in the second (new) set. Selection of new items in the DS condition was relatively poor and was always worse than would be expected if only the new stimuli had been searched. In contrast, selection of the new items in the VM condition was good and was equal to what would be expected if there had been an exclusive search of the new stimuli. These results were not altered when differences in Set 1 difficulty, task switching, and response generation were controlled for. We conclude that the mechanism of VM is distinct from mnemonic and/or serial inhibition-of-return processes as involved in search, although we also discuss possible links to more global and flexible inhibition-of-return processes not necessarily related to search.     

Nociceptive sensitivity and control: hypo- and hyperalgesia under two different modes of coping

Effects of perceived control on nociceptive sensitivity were investigated in an experimental arrangement with N = 40 healthy volunteers in which the duration of painful pressure stimuli was made contingent on success in a tracking task. Perceived control over the pain duration was manipulated through varying the frequency of success in the tracking task. The amount of painful stimulation applied in the high and low control conditions was balanced by a yoked-control design. Pain sensitivity was measured before and after the tracking task by means of a thermal sensory analyzer. Pain sensitivity was found to decrease in the low control condition (hypoalgesia), and to increase slightly in the high control condition (hyperalgesia). These effects are explained with reference to a dual process model of coping.     

... In relation to mental health

Pastoral Psychology -     

The neural correlates of implicit and explicit sequence learning: Interacting networks revealed by the process dissociation procedure

In two H2(15)O PET scan experiments, we investigated the cerebral correlates of explicit and implicit knowledge in a serial reaction time (SRT) task. To do so, we used a novel application of the Process Dissociation Procedure, a behavioral paradigm that makes it possible to separately assess conscious and unconscious contributions to performance during a subsequent sequence generation task. To manipulate the extent to which the repeating sequential pattern was learned explicitly, we varied the pace of the choice reaction time task-a variable that is known to have differential effects on the extent to which sensitivity to sequence structure involves implicit or explicit knowledge. Results showed that activity in the striatum subtends the implicit component of performance during recollection of a learned sequence, whereas the anterior cingulate/mesial prefrontal cortex (ACC/MPFC) supports the explicit component. Most importantly, we found that the ACC/MPFC exerts control on the activity of the striatum during retrieval of the sequence after explicit learning, whereas the activity of these regions is uncoupled when learning had been essentially implicit. These data suggest that implicit learning processes can be successfully controlled by conscious knowledge when learning is essentially explicit. They also supply further evidence for a partial dissociation between the neural substrates supporting conscious and nonconscious components of performance during recollection of a learned sequence.     

Dissociable contributions within the medial temporal lobe to encoding of object-location associations

The crucial role of the medial temporal lobe (MTL) in episodic memory is well established. Although there is little doubt that its anatomical subregions-the hippocampus, peri-, entorhinal and parahippocampal cortex (PHC)-contribute differentially to mnemonic processes, their specific functions in episodic memory are under debate. Data from animal, human lesion, and neuroimaging studies suggest somewhat contradictory perspectives on this functional specialization: a general participation in declarative memory, an exclusive involvement in associative mnemonic processes, and a specific contribution to spatial memory are reported for the hippocampus, adjacent cortices, and the PHC. A functional lateralization in humans dependent on the verbalizability of the material is also discussed herein. To further elucidate the differential contributions of the various MTL subregions to encoding, we employed an object-location association memory paradigm. The memory for each of the studied associations was tested twice: by the object, and by the location serving as retrieval cue. The memory accuracy in response to both cue types was also assessed parametrically. Brain activity during encoding which leads to different degrees of subsequent memory accuracy under the two retrieval conditions was compared. We found the bilateral posterior PHC to participate in encoding of both the object associated with a location and the location associated with an object. In contrast, activity in an area in the left anterior PHC and the right anterior MTL was only correlated with the memory for the location associated with an object.     

Negative priming with masked distractor-only prime trials: awareness moderates negative priming

The literature yields inconsistent evidence for negative priming (NP) following masked distractor-only prime trials. We contrast two different hypotheses on the inconsistent findings: one - which is most compatible with the temporal discrimination theory - that relates the sign of priming effects to the absence vs. presence of prime awareness and one -which is most compatible with the inhibition and episodic retrieval accounts - that relates the sign of priming effects to the prime event being categorized as a to-be-attended vs. to-be-ignored event. In two experiments, it turned out that participants' awareness of the masked stimuli caused the different results (with participants being not aware of the primes showing NP), whereas the factor prime color = probe target color vs. prime color = probe distractor color (i.e., the prime contains the to-be-attended vs. the to-be-ignored signal) did not moderate NP. These findings are discussed with regard to theories of negative priming and the debate on conscious vs. unconscious perception.     

Lexically-driven syntactic priming

Syntactic priming studies demonstrate that exposure to a particular syntactic structure leads speakers to reproduce the same structure in subsequent utterances. Explanations for this phenomenon rely on either the retrieval of morphosyntactic features associated with the verb in the prime sentence or the preservation of the mapping between message and word sequences in the prime sentence. Two experiments test the featural account of syntactic priming. We used single word primes to investigate the dative alternation in German (Experiment 1) and Dutch (Experiment 2). Native speakers read ditransitive verbs that are restricted either to the prepositional (dative) or double object construction, followed by pictures that can be described with either structure. We find that a single verb in isolation is sufficient to bias speakers' production preferences supporting lexically-driven accounts of syntactic priming.     

Priming a new identity: self-monitoring moderates the effects of nonself primes on self-judgments and behavior

When a construct is primed, people often act in construct-consistent ways. Several accounts for this effect have been offered, including ideomotor theory and a social functional perspective. The authors tested an additional perspective, the Active-Self account, whereby primes can temporarily alter self-perceptions. In Study 1, non-African American participants reported feeling more aggressive on an implicit measure following an African American prime. In Study 2, participants reported feeling luckier on an implicit measure following a number 7 (vs. 13) prime. In both studies, these effects were obtained only for low self-monitors, who are more likely to change self-conceptions in response to diagnostic self-information and to use their internal states in guiding behavior. Study 3 showed that low self-monitors also show larger behavioral effects of primes.