Interpreting dissociations between regular and irregular past-tense morphology: Evidence from event-related potentials

Neuropsychological dissociations between regular and irregular English past-tense morphology have been reported using a lexical decision task in which past-tense primes immediately precede present-tense targets. We present N400 event-related potential data from healthy participants using the same design. Both regular and irregular past-tense forms primed corresponding present-tense forms, but with a longer duration for irregular verbs. Phonological control conditions suggested that differences in formal overlap between prime and target contribute to, but do not account for, this difference, suggesting a link between irregular morphology and semantics. Further analysis dividing the irregular verbs into two categories (weak irregular and strong) revealed that priming for strong verbs was reliably stronger than that for weak irregular and regular verbs, which were statistically indistinguishable from one another. We argue that, although we observe a regular-irregular dissociation, the nature of this dissociation is more consistent with single- than with dual-system models of inflectional morphology.     

Neural activity in relation to temporal distance: Differences in past and future temporal discounting

This study investigated the differences between past and future temporal discounting in terms of neural activity in relation to temporal distance. Results show that brain regions are engaged differently in past and future temporal discounting. This is likely because past temporal discounting requires memory reconstruction, whereas future temporal discounting requires the processing of uncertainty about the future. In past temporal discounting, neural activity differed only when preferences were made between rewards received one hour prior and rewards received further in the past. The peak amplitudes of P2 and P3 varied as the temporal distance increased from 2 weeks to 50 years. In future temporal discounting, neural activity differed only when preferences were evaluated between two delayed rewards. The delay conditions (6 months:5 years) and (6 months:50 years) had a significant influence on P2 and N2. Findings indicate the existence of different decision-making systems operating in past and future temporal discounting.     

On the processing of regular and irregular forms of verbs and nouns: evidence from neuropsychology

Following acquired brain damage, a native English speaking patient (AW) encountered problems accessing phonology in speech production, while her ability to access word meaning appeared to be intact. In a series of tasks, AW was presented either with a verb, and was asked to produce its past tense or past participle (walk --> "walked"), or with a noun, and was asked to produce its plural (glove --> "gloves"). A stark dissociation was found: while AW responded accurately with regular forms of verbs (walked) and nouns (gloves), performance was significantly less accurate with irregular forms (found; children). The appearance of a selective deficit for irregular forms in conditions of impaired lexical access is in line with dual-mechanism accounts, which proposes that irregular forms are specified in the lexicon whereas regular forms are computed via rule-based mechanisms. In contrast, AW's data are problematic for connectionist accounts that do not posit separate mechanisms for processing regular and irregular forms, including the connectionist model recently proposed by Joanisse and Seidenberg (Proceedings of the National Academy of Sciences USA 96 (1999) 7592) which successfully simulated a variety of earlier neuropsychological findings. Analyses of AW's responses shed light on further details of the representation and processing of regular and irregular inflected forms.     

Alcohol intoxication alters cognitive skills mediated by frontal and temporal brain regions

Alcohol intoxication affects frontal and temporal brain areas and may functionally impair cognitive processes mediated by these regions. This study examined this hypothesis by testing the effects of alcohol on sustained attention, impulsivity, and verbal memory. Sober and placebo control groups were used to distinguish pharmacological from expectancy effects of alcohol. One hundred nine university students were assigned to an alcohol (low, medium, or high dose), placebo or sober group. Moderate and high doses of alcohol impaired all cognitive measures. A gender effect was revealed in that alcohol impaired sustained attention in males, but not females. Both sustained attention and verbal memory exhibited a U-shaped pattern, in that the medium-dose alcohol group showed the greatest impairment. This study adds to knowledge about the effects of alcohol intoxication on frontally- and temporally-mediated cognitive function. These findings have specific relevance for heavy-drinking undergraduate populations, particularly in light of the fact that repeated alcohol administration produces persistent changes in brain neurocircuitry.     

Neural correlates of temporal auditory processing in developmental dyslexia during German vowel length discrimination: an fMRI study

This fMRI study investigated phonological vs. auditory temporal processing in developmental dyslexia by means of a German vowel length discrimination paradigm (Groth, Lachmann, Riecker, Muthmann, & Steinbrink, 2011). Behavioral and fMRI data were collected from dyslexics and controls while performing same-different judgments of vowel duration in two experimental conditions. In the temporal, but not in the phonological condition, hemodynamic brain activation was observed bilaterally within the anterior insular cortices in both groups and within the left inferior frontal gyrus (IFG) in controls, indicating that the left IFG and the anterior insular cortices are part of a neural network involved in temporal auditory processing. Group subtraction analyses did not demonstrate significant effects. However, in a subgroup analysis, participants performing low in the temporal condition (all dyslexic) showed decreased activation of the insular cortices and the left IFG, suggesting that this processing network might form the neural basis of temporal auditory processing deficits in dyslexia.     

The role of visual and auditory temporal processing in reading irregular and nonsense words.

In the present study, the role of rapid visual and auditory temporal processing in reading irregular and nonsense words was investigated with a group of normal readers. One hundred and five undergraduates participated in various visual and auditory temporal-processing tasks. Readers who primarily adopted the phonological route in reading (nonsense-word readers) showed a trend for better auditory temporal resolution but readers who primarily adopted sight word skills (irregular-word readers) did not exhibit better visual temporal resolution. Both the correlation and stepwise multiple-regression analyses, however, revealed a relationship between visual temporal processing and irregular-word reading as well as a relationship between auditory temporal processing and nonsense-word reading. The results support the involvement of visual and auditory processing in reading irregular and nonsense words respectively, and were discussed with respect to recent findings that only dyslexics with phonological impairment will display temporal deficits. Further, the temporal measures were not effective discriminants for the reading groups, suggesting a lack of association between reading ability and the choice of reading strategy.     

Neural responses to meaningless pseudosigns: evidence for sign-based phonetic processing in superior temporal cortex

To identify neural regions that automatically respond to linguistically structured, but meaningless manual gestures, 14 deaf native users of American Sign Language (ASL) and 14 hearing non-signers passively viewed pseudosigns (possible but non-existent ASL signs) and non-iconic ASL signs, in addition to a fixation baseline. For the contrast between pseudosigns and baseline, greater activation was observed in left posterior superior temporal sulcus (STS), but not in left inferior frontal gyrus (BA 44/45), for deaf signers compared to hearing non-signers, based on VOI analyses. We hypothesize that left STS is more engaged for signers because this region becomes tuned to human body movements that conform the phonological constraints of sign language. For deaf signers, the contrast between pseudosigns and known ASL signs revealed increased activation for pseudosigns in left posterior superior temporal gyrus (STG) and in left inferior frontal cortex, but no regions were found to be more engaged for known signs than for pseudosigns. This contrast revealed no significant differences in activation for hearing non-signers. We hypothesize that left STG is involved in recognizing linguistic phonetic units within a dynamic visual or auditory signal, such that less familiar structural combinations produce increased neural activation in this region for both pseudosigns and pseudowords.     

Processing of Spanish Preterite regular and irregular verbs: the role of neighborhood density

Research into lexical processes shows that frequency and phonological similarity (neighborhood density) affect word processing and retrieval. Previous studies on inflectional morphology have examined the influence of frequency of occurrence in speech production on the inflectional verb paradigm in English. Limited work has been done to examine the influence of phonological similarity in languages with a more complex morphological system than English. The present study examined the influence of neighborhood density on the processing of Spanish Preterite regular and irregular verbs as produced by thirty native speakers of Spanish. The results of a naming task showed that regular verbs were processed faster and more accurately than irregular ones. Similar to what has been observed in English, a facilitative effect of neighborhood density for -ir verbs was observed in both regular and irregular verbs, such that -ir verbs with dense neighborhoods were produced faster and more accurately than -ir verbs with sparse neighborhoods. However, no neighborhood density effects were observed for -ar verbs (regular and irregular) in reaction times and accuracy rates. Thus, the activation of a specific -ir verb was facilitated by similar sounding verbs regardless of being regular and irregular. Implications for models of morphology language processing are discussed.     

Sensitivity to event timing in regular and irregular sequences: Influences of musical skill

In two experiments, the performance of listeners with different amounts of musical training (high skill, low skill) was examined in a two-alternative forced choice time-detection task involving simple five-cycle acoustic sequences. In each of a series of trials, all listeners determined which of two pattern cycles contained a small time change. Sequence context was also varied (regular vs. irregular timing). In Experiment 1, in which context was manipulated as a between-subjects variable, high-skill listeners performed significantly better than low-skill listeners only with regular patterns. In Experiment 2, in which context was manipulated as a within-subjects variable, the only significant source of variance was pattern context: All listeners were better at detecting time changes in regular than in irregular patterns. The results are considered in light of several hypotheses, including the expectancy/contrast model (Jones & Boltz, 1989).     

Shadows of the past: temporal retrieval effects in recognition memory

We examine whether temporally defined associations play a role in item recognition. The role of these associations in recall tasks is well known; we demonstrate an important role in item recognition as well. In this study, subjects were significantly more likely to recognize a test item as having been previously experienced if the preceding test item was studied in a temporally proximal list position than if the preceding test item came from a more distant list position. Further analyses showed that this associative effect was almost entirely due to cases in which the preceding test item received a highest-confidence recognition judgment.     

Neural representations during sleep: from sensory processing to memory traces

In the course of a day, the brain undergoes large-scale changes in functional modes, from attentive wakefulness to the deepest stage of sleep. The present paper evaluates how these state changes affect the neural bases of sensory and cognitive representations. Are organized neural representations still maintained during sleep? In other words, despite the absence of conscious awareness, do neuronal signals emitted during sleep contain information and have a functional relevance? Through a critical evaluation of the animal and human literature, neural representations at different levels of integration (from the most elementary sensory level to the most cognitive one) are reviewed. Recordings of neuronal activity in animals at presentation of neutral or significant stimuli show that some analysis of the external word remains possible during sleep, allowing recognition of behaviorally relevant stimuli. Event-related brain potentials in humans confirm the preservation of some sensory integration and discriminative capacity. Behavioral and neuroimaging studies in humans substantiate the notion that memory representations are reactivated and are reorganized during post-learning sleep; these reorganisations may account for the beneficial effects of sleep on behavioral performance. Electrophysiological results showing replay of neuronal sequences in animals are presented, and their relevance as neuronal correlates of memory reactivation is discussed. The reviewed literature provides converging evidence that structured neural representations can be activated during sleep. Which reorganizations unique to sleep benefit memory representations, and to what extent the operations still efficient in processing environmental information during sleep are similar to those underlying the non-conscious, automatic processing continually at work in wakefulness, are challenging questions open to investigation.     

Comparing language lateralization determined by dichotic listening and fMRI activation in frontal and temporal lobes in children with epilepsy

We investigated the relationship between ear advantage scores on the Fused Dichotic Words Test (FDWT), and laterality of activation in fMRI using a verb generation paradigm in fourteen children with epilepsy. The magnitude of the laterality index (LI), based on spatial extent and magnitude of activation in classical language areas (BA 44/45, 21/22, 39) differed significantly for patients classified with unilateral left, compared to bilateral, language representation based on FDWT scores. Concordance with fMRI was higher for those classified with unilateral left, than bilateral language representation on the FDWT. Of note, asymmetry in temporal lobe, rather than frontal lobe, activation was more strongly related to the LI from the dichotic listening test. This study shows that the FDWT can provide a quick and valid estimate of lateralization in pre-surgical candidates, which can be readily adopted for other clinical or research purposes when an estimate of language dominance is desired.     

Imaging the medial temporal lobe: exploring new dimensions

Cognitive scientists have used developments in functional imaging to explore the role of the medial temporal lobe (MTL) in memory formation. Lesion studies have suggested that separate MTL subregions make distinct contributions to memory. Functional imaging of these distinct contributions, however, remains a challenge, because the proximity of the MTL substructures tests the spatial resolution limits of current techniques. Recent findings using electrophysiological measures of neural activity highlight the importance of using information from other imaging modalities. Integrating the different modalities of neuroimaging with lesion studies, and, further, combining modalities within experiments, will provide new insights into the function of MTL subregions.     

Reward feedback processing in children and adolescents: Medial frontal theta oscillations

We examined event-related electroencephalography (EEG) oscillations, including event-related spectral perturbations (ERSP) and intertrial coherence (ITC), to compare feedback processing during a chance-based reward vs. non-reward task in groups of 10–12-year-old (n = 42), 13–14-year-old (n = 34) and 15–17-year-olds (n = 32). Because few, if any studies have applied these analytic methods to examine feedback processing in children or adolescents, we used a fine-grained approach that explored one half hertz by 16 ms increments during feedback (no win vs. win events) in the theta (4–8 Hz) frequency band. Complex wavelet frequency decomposition revealed that no win feedback was associated with enhanced theta power and phase coherence. We observed condition and age-based differences for both ERSP and ITC, with stronger effects for ITC. The transition from childhood to early adolescence (13–14 yrs.) was a point of increased differentiation of ITC favoring no win vs. wins feedback and also compared to children or older adolescents, a point of heightened ITC for no win feedback (quadratic effect).     

Root versus roof: automatic activation of location information during word processing

In four experiments, participants were presented with nouns referring to entities that are associated with an up or down location (e.g., roof, root). The required response either was compatible with the referent location or was not (e.g., upward vs. downward movement after reading roof). Across experiments, we manipulated whether the experimental task required word reading or not, as well as whether the response involved a movement or was stationary. In all experiments, participants’ responses were significantly faster in the compatible than in the incompatible condition. This strongly suggests that location information is automatically activated when nouns are being processed.     

Relations among regular and irregular morphologically related words in the lexicon as revealed by repetition priming

Several experiments examined repetition priming among morphologically related words as a tool to study lexical organization. The first experiment replicated a finding by Stanners, Neiser, Hernon, and Hall (Journal of Verbal Learning and Verbal Behavior, 1979,18, 399-412), that whereas inflected words prime their unaffixed morphological relatives as effectively as do the unaffixed forms themselves, derived words are effective, but weaker, primes. The experiment also suggested, however, that this difference in priming may have an episodic origin relating to the less formal similarity of derived than of inflected words to unaffixed morphological relatives. A second experiment reduced episodic contributions to priming and found equally effective priming of unaffixed words by themselves, by inflected relatives, and by derived relatives. Two additional experiments found strong priming among relatives sharing the spelling and pronunciation of the unaffixed stem morpheme, sharing spelling alone, or sharing neither formal property exactly. Overall, results with auditory and visual presentations were similar. Interpretations that repetition priming reflects either repeated access to a common lexical entry or associative semantic priming are both rejected in favor of a lexical organization in which components of a word (e.g., a stem morpheme) may be shared among distinct words without the words themselves, in any sense, sharing a “lexical entry.”     

Traces of times past: Representations of temporal intervals in memory

Theories of time perception typically assume that some sort of memory represents time intervals. This memory component is typically underdeveloped in theories of time perception. Following earlier work that suggested that representations of different time intervals contaminate each other (Grondin, 2005; Jazayeri & Shadlen, 2010; Jones & Wearden, 2004), an experiment was conducted in which subjects had to alternate in reproducing two intervals. In two conditions of the experiment, the duration of one of the intervals changed over the experiment, forcing subjects to adjust their representation of that interval, while keeping the other constant. The results show that the adjustment of one interval carried over to the other interval, indicating that subjects were not able to completely separate the two representations. We propose a temporal reference memory that is based on existing memory models (Anderson, 1990). Our model assumes that the representation of an interval is based on a pool of recent experiences. In a series of simulations, we show that our pool model fits the data, while two alternative models that have previously been proposed do not.     

Construal level and temporal judgments of the past: the moderating role of knowledge

The vast majority of work in construal level theory has found a robust relationship between construal level and temporal judgments for future events: Distance is associated with the abstract, and nearness is associated with the concrete. Our work looks at the past and proposes a critical moderator that reverses this relationship: knowledge. Through experiments involving real news events, we demonstrate that people with less knowledge about events felt nearer to them when recalling them in a concrete mindset versus an abstract one. However, this relationship reverses for those with greater knowledge: They feel closer to past events when recalling them in an abstract mindset versus a concrete one. We provide evidence that this reversal stems from feelings of metacognitive ease that inform temporal judgments when knowledge (which drives what information is held available and accessible in memory) and construal mindset (which drives what information is sought from memory) coincide. Our findings suggest that in memory, there are instances where the abstract seems near and the concrete seems distant.     

Implicit word activation during prerecognition processing: False recognition and remember/know judgments

Recognition memory for spoken words is influenced by phonetic resemblance between test words and items presented during study. Presentation of derived nonwords (e.g., /d/ransparent or transparen/d/) on a study list produces a higher than normal false recognition rate to base words (e.g., transparent). Test words that share beginning phonemes with studied nonwords have more false recognitions than do those that share ending phonemes. The latter difference has been attributed to familiarity resulting from prerecognition processing of spoken stimuli. As a listener hears/traens/, "transparent" may be activated as a potential solution. In the present experiments, we minimized contributions of postrecognition processing to this phenomenon by presenting a semantically unrelated test word (transportation) that was also expected to be activated during prerecognition stages of processing. The results indicated that false recognition was increased for words presumed to be activated only during prerecognition processing. Remember (R) and know (K) judgments revealed that the majority of studied words were R, and the majority of false recognitions were K. The lowest proportion of R judgments occurred for test words that were not activated during postrecognition processing (e.g., transportation and control words).     

Imaging recollection and familiarity in the medial temporal lobe: a three-component model

The medial temporal lobe (MTL) plays a crucial role in supporting memory for events, but the functional organization of regions in the MTL remains controversial, especially regarding the extent to which different subregions support recognition based on familiarity or recollection. Here we review results from functional neuroimaging studies showing that, whereas activity in the hippocampus and posterior parahippocampal gyrus is disproportionately associated with recollection, activity in the anterior parahippocampal gyrus is disproportionately associated with familiarity. The results are consistent with the idea that the parahippocampal cortex (located in the posterior parahippocampal gyrus) supports recollection by encoding and retrieving contextual information, whereas the hippocampus supports recollection by associating item and context information. By contrast, perirhinal cortex (located in the anterior parahippocampal gyrus) supports familiarity by encoding and retrieving specific item information. We discuss the implications of a 'binding of item and context' (BIC) model for studies of recognition memory. This model argues that there is no simple mapping between MTL regions and recollection and familiarity, but rather that the involvement of MTL regions in these processes depends on the specific demands of the task and the type of information involved. We highlight several predictions for future imaging studies that follow from the BIC model.