The formation of the past tense of verbs in English has been the focus of the debate concerning connectionist vs. symbolic accounts of language. Brain-injured patients differ with respect to whether they are more impaired in generating irregular past tenses (TAKE-TOOK) or past tenses for nonce verbs (WUG-WUGGED). Such dissociations have been taken as evidence for distinct ''rule'' and ''associative'' memory systems in morphology and against the connectionist approach in which a single system is used for all forms. We describe a simulation model in which these impairments arise from damage to phonological or semantic information, which have different effects on generalization and irregular forms, respectively. The results provide an account of the bases of impairments in verb morphology and show that these impairments can be explained within connectionist models that do not use rules or a separate mechanism for exceptions.

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Developmental deficits may be specific to language or working memory, or include impairments in both areas. Sentence recall is a useful clinical marker of SLI and combined language and working memory impairments.

Behavioral and modeling evidence suggests that words compete for recognition during auditory word identification, and that phonological similarity is a driving factor in this competition. The present study used event-related potentials [ERPs] to examine the temporal dynamics of different types of phonological competition (i.e., cohort and rhyme). ERPs were recorded during a novel picture-word matching task, where a target picture was followed by an auditory word that either matched the target (CONE-cone), or mismatched in one of three ways: rhyme (CONE-bone), cohort (CONE-comb), and unrelated (CONE-fox). Rhymes and cohorts differentially modulated two distinct ERP components, the Phonological Mismatch Negativity [PMN] and the N400, revealing the influences of pre-lexical and lexical processing components in speech recognition. Cohort mismatches resulted in late increased negativity in the N400, reflecting disambiguation of the later point of miscue and the combined influences of top-down expectations and misleading bottom-up phonological information on processing. In contrast, we observed a reduction in the N400 for rhyme mismatches, reflecting lexical activation of rhyme competitors. Moreover, the observed rhyme effects suggest that there is interaction between phoneme-level and lexical-level information in the recognition of spoken words. The results support the theory that both levels of information are engaged in parallel during auditory word recognition in a way that permits both bottom-up and top-down competition effects. Keywords Perception; Auditory processing; Event related potentialsIn understanding spoken language listeners need to both perceive incoming auditory information and access a semantic representation of that input. Although speech is understood quite rapidly and effortlessly, the cognitive processing involved in spoken word recognition is not trivial. In order to recognize what is being said, acoustic information must be translated into a phonological code, segmented into discrete words, and integrated with both the immediate context and prior knowledge such as word familiarity and contextual CIHR Author ManuscriptCIHR Author Manuscript CIHR Author Manuscript cues. Consistent with this, studies have revealed a range of factors that influence auditory word recognition (Luce & Pisoni, 1998;Norris, McQueen, & Cutler, 2000;Frauenfelder & Tyler, 1987;McClelland & Elman, 1986). These can be coarsely divided into two categories: those revealing the influence of 'pre-lexical' cues related to acoustic and phonological features, and those indexing the role of 'lexical' knowledge that denotes lexical-level influences such as frequency. There is significant ongoing discussion about exactly how auditory words are recognized, focusing on how and when these different types of information are accessed during the time course of processing, and furthermore, the extent to which these interact.Evidence suggests that spoken words are processed as speech unfolds, and that phonologically similar items ...

Two decades of research conducted to date has examined selective visual attention to threat and reward stimuli as a function of individual differences in anxiety using the dot-probe task. The present study tests a connectionist neural-network model of meta-analytic and key individual study results derived from this literature. Attentional bias for threatening and reward-related stimuli is accounted for by connectionist model implementation of the following clinical psychology and affective neuroscience principles: 1) affective learning and temperament, 2) state and trait anxiety, 3) intensity appraisal, 4) affective chronometry, 5) attentional control, and 6) selective attention training. Theoretical implications for the study of mood and anxiety disorders are discussed.Key Words: Dot-Probe Task, Selective Attention, Threat, Reward, Anxiety, Depression, Connectionism, Neural Network, Amygdala. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTSelective Attention for Reward & Threat 3 Selective Attention to Threat versus Reward: Meta-analysis and Neural-Network Modeling of the Dot-Probe TaskTheoretical constructs and research methodologies derived from cognitive psychology figure prominently in current emotion research, including investigations into the nature and function of anxiety. For example, cognitive researchers have been studying how individuals visually attend to threatening stimuli, and how between-subject variability in the functioning of attentional systems may correlate with individual differences in anxiety-related traits and disorders (e.g., Williams, Watts, MacLeod, & Matthews, 1997).Evolutionary models of emotion and attention hypothesize that nature may have programmed the visual-attention system to attend selectively to stimuli of biological significance, including both to cues of possible impending threat (e.g., predators), on the one hand, and to cues of potential reinforcement-reward value (e.g., food, mates), on the other (e.g., LeDoux, 1996;Panksepp, 1998;Rolls, 1999). Attentional mechanisms procuring the rapid detection of sources of potential environmental threat are therefore presumed to afford an obvious survival-facilitating mechanism (A. Mathews & Mackintosh, 1998;A. Mathews, Mackintosh, & Fulcher, 1997;. However, an equally integral attentional function to the biological fitness of organisms is to orient toward stimuli of potential reward-value in their environments (Panksepp, 1998;Rolls, 1999).It may be that reward-and threat-detection are performed by distinct attentional systems 1 . Specifically, threat detection attentional mechanisms may represent secondary interrupt programs that continuously perform a background analysis of stimuli regarding their likelihood of representing a source of danger, attaining foreground and conscious significance only to the extent that this analysis results in the detection of relatively significant sources of danger (e.g., LeDoux, 1996). Otherwise, the default and primary orientation of attention may be toward reward-relevant stimuli...

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