Neural Representations and Mechanisms for the Performance of Simple Speech Sequences

“Such multiplicative or shunting terms (Grossberg, 1973) are motivated by empirically observed cell membrane properties (e.g., Hodgkin & Huxley, 1952).”

“More recent neural network models (Beiser & Houk, 1998; Elman, 1990; Lewandowsky & Murdock, 1989; Jordan, 1986) proposed revisions that rely”

“The organization of BG circuits into largely parallel loops (Alexander & Crutcher, 1990; Alexander et al., 1986) offers one possible substrate for the cascaded processing stages that enable linguistic selections from competing alternatives; these selections (cf. choice layer activations) can then…”

“These properties help explain why there is a low limit (see Cowan, 2000) to the number of items that can be planned in working memory and recalled in the correct order.”

“SSM representations are functionally similar to a mental syllabary (Levelt & Wheeldon, 1994; Crompton, 1982), suggested by Levelt et al. (1999) to consist of a “repository of gestural scores for the frequently used syllables of the language” (p. 5).”

“Such models generally follow the theoretical work of Levelt ( 1989 ), Garrett ( 1975 ), and others.”

“Interactions between the cortex and the BG are organized into multiple loop circuits (Middleton & Strick, 2000; Alexander & Crutcher, 1990; Alexander, DeLong, & Strick, 1986).”

“Similarly, Dell (1986) speculated that a principle explanation for the appearance of speech errors in normal speech is the speakerʼs need for productivity or generativity.”

“These recording sites were within approximately 5 mm of the ventral portion of the arcuate sulcus, which has been proposed to be homologous to the IFS in humans (Rizzolatti & Arbib, 1998).”

“Mink (1996) and Mink and Thach (1993) outlined a conceptual model of BG function, suggesting that BG loops are used to selectively enable a motor program for output among competing alternatives.”

“The architecture within BG loops is intricate (eg, Parent & Hazrati, 1995 ), but here we adopt a simplified view to limit the model's overall complexity.”

“The medial frontal cortex, consisting of the more posterior SMA and the more anterior pre-SMA (Picard & Strick, 1996; Matsuzaka, Aizawa, & Tanji, 1992), has been implicated in sequencing and speech production tasks.”

“Learning rules that conserve total synaptic strength have been proposed elsewhere (Grossberg, 1976;von der Malsburg, 1973), and similar conservational principles have been observed empirically (Markram & Tsodyks, 1996).”

“The medial frontal cortex, consisting of the more posterior SMA and the more anterior pre-SMA (Picard & Strick, 1996; Matsuzaka, Aizawa, & Tanji, 1992), has been implicated in sequencing and speech production tasks.”

“A similar region in left dorsal inferior frontal gyrus has been suggested to be involved in sequencing discrete units, including phonemes (Gelfand&Bookheimer, 2003), and in phonological encoding tasks (Papoutsi et al., 2009; Chein & Fiez, 2001; Burton, Small, & Blumstein, 2000; Poldrack et al., 1999).”

“Learning rules that conserve total synaptic strength have been proposed elsewhere (Grossberg, 1976; von der Malsburg, 1973), and similar conservational principles have been observed empirically (Markram & Tsodyks, 1996).”

“Un co rre cte d Pr oo f stereotyped, however, readout by serial or “synfire” chains (e.g., Pulvermüller, 1999, 2002; Abeles, 1991) can offer greater efficiency.”

“More recent neural network models (Beiser & Houk, 1998; Elman, 1990; Lewandowsky & Murdock, 1989; Jordan, 1986) proposed revisions that rely”

“Such loops may be nested to account for various levels of language production (e.g., Ward, 1994; Garrett, 1975).”

“MacNeilage (1998) has proposed that speech evolved the capability to program syllabic frames with phonological content elements and that every speaker learns to make use of this capacity during his or her own period of speech acquisition.”

“The SSM is a component of the DIVA model (Guenther et al., 1998, 2006; Guenther, 1995) that is hypothesized to contain cells that, when activated, “readout” motor programs and sensory expectations for well-learned speech sounds.”

“Learning rules that conserve total synaptic strength have been proposed elsewhere (Grossberg, 1976; von der Malsburg, 1973), and similar conservational principles have been observed empirically (Markram & Tsodyks, 1996).”

“…but less prevalent (only 2–3% of striatal cells in rats, but perhaps as many as 23% in humans; Graveland, 1985), are heterogeneous interneurons, many of which exhibit resting firing rates and receive cortical, thalamic, and dopaminergic input (Tepper, Koos, & Wilson, 2004; Kawaguchi, 1993).”

“Because total activity growth is a decelerating and saturating function of the number of planned items in a sequence, relative activation levels become more difficult to distinguish, and more readily corrupted by noise (Page & Norris, 1998), in longer sequences.”

“də,” an example of a simple exchange error that obeys syllable position constraints as noted in previous studies (e.g. MacKay, 1970; Shattuck-Hufnagel, 1979).”

“Vousden et al. (2000) presented a similarly motivated model that is derived from a previous proposal for serial recall (Brown et al., 2000).”

“Recent models within this lineage hypothesize order to be accounted for by some contextual signal such as the state of an oscillatory circuit or other time-varying function (Brown, Preece, &Hulme, 2000; Vousden, Brown,&Harley, 2000; Burgess & Hitch, 1999; Henson, 1998).”

“Construction of the model was guided by previous theoretical work as well as clinical and experimen- tal results, most notably a companion fMRI study (Bohland & Guenther, 2006).”

“Rank-order-selective cells have also been found, primarily in the pre-SMA, whose activity increased before the nth movement in the sequence, regardless of the particular movement (see also Clower & Alexander, 1998).”

“This input is thresholded by θq, and amplified via a faster-than-linear activation function, y(x) =x2 (Grossberg, 1973).”

“Such action selection models (also Gurney, Prescott, & Redgrave, 2001a , 2001b ; Kropotov & Etlinger, 1999 ; Redgrave, Prescott, & Gurney, 1999 ), which suggest that the BG do not generate movements but rather select and enable them, are relevant for sequence performance.”

“Construction of the model was guided by previous theoretical work as well as clinical and experimen- tal results, most notably a companion fMRI study (Bohland & Guenther, 2006).”

“The WEAVER (and later WEAVER++) model (Levelt et al., 1999; Roelofs, 1997) is broadly a computer implementation of the Nijmegen model.”

“…in which frequently encountered syllables are produced with a shorter latency than uncommon (but well-formed) syllables, has been reported by several researchers (Cholin, Levelt, & Schiller, 2006; Laganaro & Alario, 2006; Alario et al., 2004; Carreiras & Perea, 2004; Levelt & Wheeldon, 1994).”

“Crinion et al. (2006) have also suggested that the caudate may subserve selection of words from a bilingual lexicon.”

“Importantly, at around 18 months of age, the rate of word acquisition in children may quadruple (Goldfield & Reznick, 1990 ).”

“The left prefrontal cortex, specifically in and surrounding the ventral inferior frontal sulcus (IFS), showed increased activity in a memory-guided speaking task when the serial complexity of the utterance was increased (Bohland & Guenther, 2006).”

“DIVA is a neural network model of speech motor control and acquisition that offers unified explanations for a large number of speech phenomena including motor equivalence, contextual variability, speaking rate effects, and coarticulation (Guenther et al., 1998; Guenther, 1995).”

“Construction of the model was guided by previous theoretical work as well as clinical and experimen- tal results, most notably a companion fMRI study (Bohland & Guenther, 2006).”

“Finally, damage to the SSM or the interface between the IFS choice field and the SSM (e.g., damage to corticocortical projections) should lead to problems in realizing a phonetic plan or diminished ability to choose a phonetic plan; these deficits would be in line with observations in patients with AOS (Hillis et al.,…”

“Also found in the striatum, but less prevalent (only 2–3% of striatal cells in rats, but perhaps as many as 23% in humans; Graveland, 1985), are heterogeneous interneurons, many of which exhibit resting firing rates and receive cortical, thalamic, and dopaminergic input ( Tepper, Koos, & Wilson, 2004; Kawaguchi, 1993).”

“DIVA is a neural network model of speech motor control and acquisition that offers unified explanations for a large number of speech phenomena including motor equivalence, contextual variability, speaking rate effects, and coarticulation (Guenther et al., 1998; Guenther, 1995).”

“, 2000), and both structural and functional abnormalities have been observed in the caudate in patients with inherited verbal dyspraxia characterized by particular difficulties with complex speech sequences (Vargha-Khadem et al., 1998; Watkins et al., 2002).”

“…are based on integrating the sparse available data from clinical and functional imaging studies and from inferences drawn from nonspeech sequencing tasks in other species, under the assumption that similar mechanisms should underlie linguistic processes and other complex serial behaviors.”

“These findings suggest differential roles for the pre-SMA and SMA in speech, which has also been demonstrated elsewhere (Alario, Chainay, Lehericy, & Cohen, 2006 ).”

“, 2000), and both structural and functional abnormalities have been observed in the caudate in patients with inherited verbal dyspraxia characterized by particular difficulties with complex speech sequences (Vargha-Khadem et al., 1998; Watkins et al., 2002).”

“Medium spiny neurons send inhibitory projections to cells in the pallidum including the globus pallidus internal (GPi) segment, which are tonically active and inhibitory to cells in the thalamus, which in turn project back to cortex (eg, Deniau & Chevalier, 1985 ).”

“Finally, Shima and Tanji (2000) found that only 6% of pre-SMA cells were selective to particular movements as opposed to 61% of cells in the SMA, indicating a cognitivemotor functional division.”

“…in sequencing motor acts (e.g., Harrington & Haaland, 1998), and abnormalities in these regions variously impact speech production (Murdoch, 2001; Kent, 2000), with some patients having particular Bohland, Bullock, and Guenther 1507 D o w n l o a d e d f r o m h t t p : / / m i t p r c . s i l v…”

“A syllable frequency effect, in which frequently encountered syllables are produced with a shorter latency than uncommon (but well-formed) syllables, has been reported by several researchers (Cholin, Levelt, & Schiller, 2006; Laganaro & Alario, 2006; Alario et al., 2004; Carreiras & Perea, 2004; Levelt & Wheeldon, 199…”

“Mink (1996) and Mink and Thach (1993) outlined a conceptual model of BG function, suggesting that BG loops are used to selectively enable a motor program for output among competing alternatives.”

“MacKay (1970), in his study of spoonerisms, or phoneme exchange errors (e.g., saying “heft lemisphere” instead of the intended “left hemisphere”), noted the prominence of the syllable position constraint, in which exchanges are greatly biased to occur between phonemes occupying the same positional…”

“Locke (1997) presented a theory of neurolinguistic development involving four stages: (1) vocal learning, (2) utterance acquisition,”

“total activation distributed among the representation for planned items (Averbeck et al., 2002; Cisek & Kalaska, 2002).”

“Bohland and Guenther (2006) described differences between anterior and posterior medial areas, with the pre-SMA increasing activity for more complex syllable frames (e.g., CCCV3 vs. CV) and with the SMA increasing activity during overt speaking trials relative to preparationonly trials.”

“In this version of the model, we have not fully explored the parameter space to provide particularly optimal settings but reported simulations use the same parameter set (excepting noise).”

“Such delays in the production model have been considered by Guenther et al. (2006). Alternatively, in covert or internal speech, this completion signal might arrive from elsewhere, allowing the model to proceed through SSM programs without overtly articulating them.”

“We plan to explore the probable role of the cerebellum in phonological and phonetic processes (eg, Ackermann, 2008 ), including a role in on-line sequencing, for example, by fast parallel loading of phonological memory buffers (cf.”

“These correspond to a generic syllable template, such as that introduced by Fudge (1969) and used in the model of verbal STM introduced by Hartley and Houghton (1996).”

“Construction of the model was guided by previous theoretical work as well as clinical and experimen- tal results, most notably a companion fMRI study (Bohland & Guenther, 2006).”

“The proposal that two loops through the BG, one mediated by the head of the caudate nucleus and one mediated by the putamen, are important in cognitive and motor aspects of speech production, respectively, was supported by intraoperative stimulation results demonstrating dysarthria and articulatory deficits when stimu…”

“A number of concrete theoretical proposals have emerged to model serial behaviors (see Bullock, 2004; Rhodes, Bullock, Verwey, Averbeck, & Page, 2004; Houghton & Hartley, 1995).”

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“These correspond to a generic syllable template, such as that introduced by Fudge (1969) and used in the model of verbal STM introduced by Hartley and Houghton (1996).”

“A similar region in left dorsal inferior frontal gyrus has been suggested to be involved in sequencing discrete units, including phonemes (Gelfand&Bookheimer, 2003), and in phonological encoding tasks (Papoutsi et al., 2009; Chein & Fiez, 2001; Burton, Small, & Blumstein, 2000; Poldrack et al., 1999).”

“Further analyses have shown a partial normalization of total activation distributed among the representation for planned items (Averbeck et al., 2002; Cisek & Kalaska, 2002).”

“Because choice of syllable frames in the pre-SMA “starts” the productionprocess, damagehere could result in reductions in self-initiated speech ( Jonas, 1981, 1987) but also may result in “frame deficiencies”— perhaps taking the form of reducing complex frame types to simpler ones.”

“Also found in the striatum, but less prevalent (only 2–3% of striatal cells in rats, but perhaps as many as 23% in humans; Graveland, 1985), are heterogeneous interneurons, many of which exhibit resting firing rates and receive cortical, thalamic, and dopaminergic input (Tepper, Koos, & Wilson,…”

“Treiman and Danis (1988) also noted that during nonword repetition, most errors are phonemic substitutions that preserve syllable structure.”

“Such action selection models (also Gurney, Prescott, & Redgrave, 2001a, 2001b; Kropotov & Etlinger, 1999; Redgrave, Prescott, & Gurney, 1999), which suggest that the BG do not generate movements but rather select and enable them, are relevant for sequence performance.”

“Vousden et al. (2000) presented a similarly motivated model that is derived from a previous proposal for serial recall (Brown et al., 2000).”

“…in which frequently encountered syllables are produced with a shorter latency than uncommon (but well-formed) syllables, has been reported by several researchers (Cholin, Levelt, & Schiller, 2006; Laganaro & Alario, 2006; Alario et al., 2004; Carreiras & Perea, 2004; Levelt & Wheeldon, 1994).”

“…are based on integrating the sparse available data from clinical and functional imaging studies and from inferences drawn from nonspeech sequencing tasks in other species, under the assumption that similar mechanisms should underlie linguistic processes and other complex serial behaviors.”

“Damage to the BG planning loop may impact selection and notably the timing of selection processes in phonological encoding, which is consistent with someobservations (Kreisler et al., 2000; Pickett et al., 1998).”

“Recently, this class of CQ models has received substantial support from direct neurophysiological recordings in monkeys (Averbeck, Chafee, Crowe, & Georgopoulos, 2003) and from chronometric analyses of seriation errors (Farrell & Lewandowsky, 2004).”

“…(in this case a sequence of the constituent syllable positions within a syllable frame) and another type that codes for a specific serial position within that sequence, are similar to cells that have been identified in the pre-SMA in monkey studies (Shima & Tanji, 2000; Clower & Alexander, 1998).”

“This is consistent with a hypothesis that this region contains a representation of a forthcoming speech plan.”

“A number of concrete theoretical proposals have emerged to model serial behaviors (see Bullock, 2004; Rhodes, Bullock, Verwey, Averbeck, & Page, 2004; Houghton & Hartley, 1995).”

“The architecture within BG loops is intricate (e.g., Parent & Hazrati, 1995), but here we adopt a simplified view to limit the modelʼs overall complexity.”

“The cerebellum may also be involved in the generation of prosody (Spencer & Slocomb, 2007), along with other structures, and future instantiations of the GODIVA model should strive to explain how prosody and stress can be encoded at the phonological and phonetic levels.”

“A shortcoming of previous theoretical psycholinguistic proposals has been their general failure to account for how linguistic behavior can emerge from specific neural structures (Nadeau, 2001).”

“Several concerns arise from the modelʼs timing, association, and recall processes; see the critiques of this class of models in Lewandowsky, Brown, Wright, and Nimmo (2006) and Agam, Bullock, and Sekuler (2005).”

“Explicit calls for bridging this latter gap have been made in the study of communication disorders (McNeil, Pratt, & Fossett, 2004;Ziegler, 2002).”

“…BG are involved in sequencing motor acts (e.g., Harrington & Haaland, 1998), and abnormalities in these regions variously impact speech production (Murdoch, 2001; Kent, 2000), with some patients having particular Bohland, Bullock, and Guenther 1507 D o w n l o a d e d f r o m h t t p : / / m i t…”

“Lesions to the medial wall cause speech problems (Pai, 1999; Ziegler, Kilian, & Deger, 1997; Jonas, 1981, 1987), usually resulting in reduced propositional speech with nonpropositional speech (e.”

“Several concerns arise from the model’s timing, association and recall processes; see the critiques of this class of models in Agam et al. (2005) and Lewandowsky, Brown, Wright, & Nimmo (2006).”

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“Such models either require the ability to “label” a positional node with a particular representation or component item or require a set of all possible representations to be available at all serial positions, which is often infeasible.”

“The BG are involved in sequencing motor acts (e.g., Harrington & Haaland, 1998), and abnormalities in these regions variously impact speech production (Murdoch, 2001; Kent, 2000), with some patients having particular Bohland, Bullock, and Guenther 1507 D o w n l o a d e d f r o m h t t p : / / m i…”

“This irreducibility was supported by the finding that very young children make far fewer slips of the tongue than adult speakers (Warren, 1986).”

“Finally, the left putamen and thalamus were incorporated into a motor loop that passes activity from the SMA via the putamen to the thalamus and into the motor cortex (Bohland et al., 2010).”

“Parallel to the unfolding of this information, a feedback control subsystem corrects for perceived deviations of the preplanned movements from their predicted goals [55, 56].”

“Further levels (and so other competitive queuing networks) are needed for actual production and to account for speech errors (see Bohland et al., 2009 for details).”