Segmental and Syllabic Processing in Healthy Younger and Older Adults: An Electrophysiological Study

Yael Neumann*, Loraine K. Obler**, Valerie Shafer**, & Hilary Gomes****Queens College, The City University of New York,

**The Graduate Center, The City University of New York, ***City College, The City University of New York (E-mail contact: ynslp@aol.com)

INTRODUCTION

Lexical access and aging•Naming problems increase in frequency with age•Difficulty lies at the phonological level due to weakened connections in memory with age, as described in the Transmission Deficit Hypothesis (TDH) (Burke et al., 1991; MacKay and Burke, 1990); however, it is unclear how phonological components are accessed.

Theoretical models of speech production•Retrieval of three types of information: conceptual-semantic, syntactic, & phonological•Two distinct processing stages (Dell and O’Seaghdha, 1992; Levelt, 2001; Levelt, Roelofs, and Meyer, 1999)

Time-course studies•Behavioral: chronometric studies of tip-of-the-tongue (TOT) states (e.g., Brown and McNeill, 1966; Burke et

al., 1991; Butterworth, 1989; Fromkin, 1973; Garrett, 1988, 1993); however, limited in identifying locus of phonological difficulty •Neuroimaging: ERP and MEG (e.g. van Turennout et al., 1997, 1998; Schmitt et al., 2000, 2001; Indefrey and Levelt,

2004); however, scant research investigating various phonological substages (Schiller, 2006; Schiller et al.,

2003) in the younger and older adult population.

PURPOSE

1) To investigate the effects of age on the phonological retrieval process2) To compare the time course of the phonological substages, segments vs. syllables

VARIABLES

Independent variables: –2 tasks (segmental vs. syllabic)–2 age-groups of healthy adult participants (younger: 23-40 years vs. older: 68-80)

Dependent variable: –Reaction time (RT)

–Event-related potential (ERP) components

METHOD

• Go/Nogo implicit picture naming tasks:1) Segment: final /n/ vs. final /r/2) Syllable: one vs. two syllables

• ERP components:1) N2d (Nogo minus Go waves)

reflects response inhibition, fronto-central sites, 251-600 ms2) P3d (Nogo minus Go waves)

reflects cognitive effort/non-specific inhibition, fronto-central sites, 601-1100 ms3) Visual-Evoked Potentials (VEPs)

reflects sensory processing, occipital sites, 100-250 ms

STIMULI

•28 colored pictures (Snodgrass and Vanderwart)Moderate frequency: mean: 37 per million (range: 6-148 per million) (Francis and Kucera,

1982)

Mean number of phonemes: 3.6 (range: 1-6 phonemes)•Same pictures used for each task, repeated 10x

7 final /n/, 1-syllable; 7 final /n/, 2-syllable; 7 final /r/, 1-syllable; 7 final /r/, 2-syllable•Total: 280 trials/task

140 go, 140 nogo10 blocks of 28 items

•Pseudo-randomize item order w/in block-No more than 3 go or 3 nogo responses consecutively-Semantic groups (e.g. foods, body parts, animals) were separated by at least 2 non-

semantically related items, to minimize semantic priming advantage.•Trial time line: “+”-------blank---- GO/NOGO decision----------blank

750 ms 750 ms 1500 ms 750 ms 

    

PARTICIPANTS •16 Younger adults (mean: 28.3 yo; range: 23-40 yo; 9 F, 7 M)16 Older adults (mean: 73.3 yo; range: 68-80 yo; 11 F, 5 M)

•Participant questionnaire to screen for:-Neurological or psychiatric illnesses-History of SL and learning difficulties-Language background (native monolingual American-English speakers,

no L2 before puberty, poor-somewhat rating of L2 post-puberty)-At least H.S. level education (participants were matched for level of

education) 

RESULTS

A. Behavioral findings1.RT mean (SD) ms:

Group Segment Syllable

Younger

Older

663 (81)

759 (90)

665 (110)

771 (90)

Suggests comparable task difficulty

2. Errors mean (SD):

Error Younger Older Segment Syllable

Omission

Commission

1.7 (2.2)

1.3 (2.2)

4.9 (5.3)

2.0 (3.6)

1.9 (1.8)

1.5 (3.3)

4.7 (5.6)

1.8 (2.7)

Suggests older group experienced more difficulty with the syllable, than segment, task

B. ERP findings

Segment task Syllable task

Red: youngerBlue: older

Grand Average (GAV)Raw wavesSite Fz7:

1) N2d latency: 1) Older > younger on both phonological tasks by 100 ms;Suggests phonological processing is more difficult with age2) In the older group: syllable > segmentSuggests that older group has more difficulty on the syllabic than segmental processing3) In the younger group: syllable = segmentSuggests parallel processing in the younger group2) P3d latency:

1) Same onset latency in both groups, yet it was significant for a longer time (200 ms) in the older, than younger, group on the segment task 2) Two-peak morphology on syllable task in younger group

P3d amplitude: 1) Older > younger only for the segment task Suggests greater cognitive effort in the older, than the younger, group, only on the

segment task2) In the older group: syllable = segment Suggests older group expends comparable cognitive effort on both tasks3) In the younger group: syllable = segment Suggests younger group expends comparable cognitive effort on both tasks

3) VEP latency: 1) Younger = older, than younger, group on the segment task Latency suggests comparable sensory processing with age, yet amplitude suggests older expended greater visual attention on both tasks

SUMMARY AND CONCLUSIONS1) Age Effects: Phonological processing: Older > Younger (100 ms) on both phonological tasks;

Syllable > Segment (50 ms). Cognitive effort: Older > Younger greater cognitive load on Segment task. Sensory processing: Older = Younger so stage-specific slowing, as per the TDH

2) Time course: Support parallel view for the two phonological substages of segment and syllable information, although in the older adults the data showed that syllabic access is affected more than segmental access