What lies beneath: A comparison of reading aloud in pure alexia and semantic dementia

Figures & data

Table 1. Demographic and background neuropsychological data for the 10 pure alexic patients included in the current study, ordered from least to most impaired according to high-frequency regular-word reading accuracy

Variable	Max.	P.M.	J.W.	J.M.	T.S.	K.W.	S.C.	J.W.F.	M.S.	A.T.	E.W.
Demographics
Age (years)	—	64	59	67	57	44	81	54	70	73	74
Years of education	—	10	11	10	10	10	11	10	10	10	10
Lesion information
Neuroimaging summary	—	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-temporal	Occipito-parietal	Occipito-temporo-parietal
Aetiology	—	PCA stroke	PCA stroke	PCA tumour resection	PCA tumour resection	MCA stroke	PCA stroke	Post aneurism PCA infarct	PCA stroke	PCA stroke	MCA stroke
Working memory
Digit span (scaled score)	18	NT	9	15	8	14	7	10	14	10	7
Visual processing
Right visual fieldimpairment^a	–	Upper quadrant	Hemianopia	Upper quadrant	Hemianopia	Hemianopia	Hemianopia	Hemianopia	Hemianopia	Upperquadrant	Hemianopia
VOSP
Incompleteletters	20	NT	19	20	19	20	18	17	16	16	19
Silhouettes	30	NT	25	18	22	19	3	24	19	13	12
Object decision	20	NT	17	17	18	20	14	19	16	17	17
Progressivesilhouettes	20	NT	8	11	5	16	NT	NT	9	9	12
Dot counting	10	NT	10	10	10	9	10	10	9	10	10
Positiondiscrimination	20	NT	20	20	18	20	17	16	19	20	20
Number location	10	NT	10	10	10	10	10	8	10	9	10
Cube analysis	10	NT	9	10	10	4	9	10	7	10	7
Semantic processing
Naming^b	64	64	59	60	40	56	59	54	45	54	45
Spoken Word to Picture Matching^b	64	NT	64	63	63	63	62	NT	62	63	57
Camel and Cactus (pictures)^b	64	64	52	61	24	NT	NT	61	47	NT	45
96 Synonyms (%)^c	96	NT	93	93	83	74	71	94	81	NT	76
Phonological processing
PALPA 2: Phonological judgement	72	NT	71	72	68	71	NT	72	71	NT	65
PALPA 15: Rhyme judgement	60	NT	57	56	56	59	NT	58	53	NT	56
Phonological segmentation^d	96	NT	96	94	87	97	NT	96	91	NT	69
Spelling
PALPA 39 Written
Short	100	NT	92	100	100	NT	NT	NT	100	NT	75
Long	100	NT	50	75	100	NT	NT	NT	75	NT	17
Reading aloud
180-item list:	—
Mean RT (ms)	—	1013	7530	5432	5158	5903	7910	6484	12,667	15,683	7010
Mean accuracy (%)	—	100	91	96	95	94	83	53	75	57	58
Length effect (ms per letter)	—	170	1299	911	1060	651	1843	1369	1650	523	2248
Length effect (% per letter)^e	—	0	0.75	−1.25	−1.25	0	−3.75	1.5	−8.75	−4	−3.25
Surface List:
High-frequency regular	42	41	41	41	40	39	36	34	32	30	29
Low-frequency regular	42	40	38	37	39	36	26	39	24	22	15
High-frequency exception	42	39	40	39	37	41	31	37	30	29	25
Low-frequency exception	42	37	28	33	34	32	16	34	20	27	26

Note: Values in italics denote abnormal performance represented by scores falling beyond two standard deviations below control performance where normative data available; for Digit Span, abnormal scores are two standard deviations below age-appropriate means (Ivnik et al., 1992). VOSP = Visual Object and Space Perception Battery (Warrington & James, 1991); PALPA = Psycholinguistic Assessments of Language Processing in Aphasia (Kay, Lesser, & Coltheart, 1992a); MCA = middle cerebral artery; PCA = posterior cerebral artery; RT = reaction time; NT = not tested; NA = not available.

^aAssessed using LernReha from Kasten, Strasburger, and Sabel (1997).

^bTests from Bozeat, Gregory, Lambon Ralph, and Hodges (2000).

^cTest from Jefferies, Patterson, Jones, and Lambon Ralph (2009).

^dTests from Patterson and Marcel (1992).

^eRepresents decrease in accuracy for each additional letter in string.

Table 2. Demographic and background neuropsychological data for the 10 semantic dementia patients included in the current study, ordered from least to most impaired according to high-frequency regular-word reading accuracy

Variable	Max.	GC6	LS3	MB1	DC1	DA1	AM4	NS2	MA6	FM8	AT6
Demographics
Age (years)	—	60	62	65	77	75	65	69	73	57	68
Years of education	—	12	13	11	8	16	16	9	13	10	19
Cognitive status
MMSE	—	NT	24	22	18	9	8	25	5	22	15
Raven's coloured	—	NT	NT	17	33	NT	30	36	NT	25	34
Working memory
Digit span (scaled score)	18	5	7	4	7	3	6	6	NT	4	9
Visual processing
Rey Immediate Copy	36	34	29	26	32	34	35	36	NT	32	36
VOSP
Incomplete letters	20	20	19	19	18	17	NT	19	NT	NT	18
Silhouettes	30	5	NT	9	1	NT	NT	NT	NT	NT	NT
Object decision	20	14	NT	13	17	18	NT	NT	NT	NT	NT
Progressive silhouettes	20	NT	NT	NT	NT	NT	NT	NT	NT	NT	NT
Dot counting	10	10	10	9	10	9	NT	10	NT	NT	10
Position discrimination	20	20	20	20	20	19	NT	20	NT	NT	20
Number location	10	8	10	7	10	10	NT	9	NT	NT	8
Cube analysis	10	10	9	8	10	8	NT	10	NT	NT	10
Semantic processing
Naming^a	64	13	34	44	20	12	0	8	10	0	5
Spoken Word to Picture Matching^a	64	35	60	58	44	50	17	42	43	59	29
Pyramids and Palm Trees (pictures)	52	NT	30	39	40	39	35	39	26	46	38
Pyramids and Palm Trees (words)	52	NT	NT	NT	30	41	30	33	26	NT	27
Category (8 categories)	—	NT	NT	25	13	4	1	19	0	0	NT
Reading aloud
Surface List:
High-frequency regular	42	41	41	40	39	39	36	36	33	32	29
Low-frequency regular	42	40	35	41	39	37	34	15	25	29	29
High-frequency exception	42	38	40	40	33	35	33	31	37	21	21
Low-frequency exception	42	20	26	32	20	28	21	7	26	15	10

Note: Values in italics denote abnormal performance represented by scores falling beyond two standard deviations below performance of a group of between 100 and 24 (depending on the test) control participants comparable in terms of age and education; for Digit Span, abnormal scores are two standard deviations below age-appropriate means (Ivnik et al., 1992); for the Raven's, abnormal performance is that below the 50th percentile for older controls in norms. NT = not tested; MMSE = Mini-Mental State Examination; VOSP = Visual Object and Space Perception battery (Warrington & James, 1991); PALPA = Psycholinguistic Assessment of Language Processing in Aphasia (Kay et al., 1992b).

^aTests from Bozeat, Lambon Ralph, et al. (2000).

Figure 1. Reading-aloud accuracy for 10 pure alexic (PA) and 10 semantic dementia (SD) patients according to frequency and regularity. Error bars represent ± standard error.

Table 3. Proportion of different error types for the 10 PA and 10 SD cases

Error type	Patient type	HFR^a	LFR^a	HFE^a	LFE^a	Total^b
Omission errors
	PA	0 (0)	.017 (.017)	0 (0)	.038 (.017)	.021 (.034)*
	SD	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)*
LARC errors
	PA	.017 (.017)	.096 (.052)	.248 (.092)	.268 (.042)	.198 (.111)*
	SD	.31 (.098)	.142 (.056)	.36 (.107)	.547 (.054)	.434 (.203)*
Visual errors
	PA	.213 (.066)	.365 (.081)	.191 (.051)	.288 (.048)	.279 (.152)**
	SD	.139 (.074)	.193 (.07)	.289 (.081)	.17 (.033)	.187 (.128)**
Letter omissions
	PA	.052 (.034)	.161 (.057)	.185 (.074)	.097 (.018)	.122 (.067)
	SD	.028 (.021)	.137 (.069)	.16 (.068)	.074 (.018)	.086 (.065)
Letter additions
	PA	.035 (.019)	.066 (.035)	.008 (.008)	0 (0)	.021 (.021)
	SD	.089 (.05)	.006 (.006)	.022 (.015)	.014 (.007)	.029 (.019)
Letter transpositions
	PA	.112 (.054)	.013 (.009)	0 (0)	.004 (.004)	.024 (.022)*
	SD	.061 (.036)	0 (0)	0 (0)	0 (0)	.007 (.012)*
Letter substitutions
	PA	.332 (.098)	.258 (.076)	.34 (.092)	.166 (.044)	.242 (.07)*
	SD	.177 (.075)	.446 (.075)	.125 (.04)	.117 (.016)	.175 (.051)*
Other errors
	PA	.24 (.129)	.024 (.01)	.029 (.015)	.139 (.034)	.093 (.069)
	SD	.197 (.1)	.077 (.032)	.044 (.021)	.078 (.015)	.083 (.054)

Note: Standard deviations are provided in parentheses. PA = pure alexia; SD = semantic dementia; LARC = legitimate alternative reading of components; HFR = high-frequency regular, HFE = high-frequency exception, LFR = low-frequency regular, and LFE = low-frequency exception.

^aProportion = error type/errors per condition.

^bProportion = error type/total errors.

*Significant group difference at p < .05, one-tailed. **Marginally significant group difference at p < .08, one-tailed.

Figure 2. Proportion of legitimate alternative reading of components (LARC) and letter (visual + transposition + substitution) errors for the 10 pure alexic (PA) and 10 semantic dementia (SD) patients. Error bars represent ± standard error.

Figure 3. Proportion of word and nonword errors for the 10 pure alexic (PA) and 10 semantic dementia (SD) patients. Error bars represent ± standard error.

Table 4. Proportion of errors of commission that were phonologically identical to another known word for the 10 PA and 10 SD cases

Patient type	HFR^a	LFR^a	HFE^a	LFE^a	Total^b
PA	.823 (.1)	.903 (.04)	.826 (.062)	.649 (.057)	.777 (.084)*
SD	.665 (.1)	.556 (.063)	.43 (.077)	.411 (.039)	.46 (.111)*

Note: Standard deviations are provided in parentheses. PA = pure alexia; SD = semantic dementia; HFR = high-frequency regular, HFE = high-frequency exception, LFR = low-frequency regular, and LFE = low-frequency exception.

^aProportion = word errors/commission errors per condition.

^bProportion = word errors/total commission errors.

*Significant group difference at p < .000005, one-tailed.

Figure 4. Visual similarity of letter substitution errors for the 10 pure alexic (PA; left) and 10 semantic dementia (SD; right) patients. Values representation proportion of all substitution errors. [To view this figure in colour, please see the online version of this journal].

Figure 5. Proportion of consonant substitution errors according to number of phonetic features (place, manner, voice, sonorance) shared between presented and reported phonemes for the 10 pure alexic (PA) and 10 semantic dementia (SD) patients.

Figure 6. Schematic representation of the loci of deficits undermining reading in pure alexic (PA; left) versus semantic dementia (SD; right) within a triangle model of reading. Filled ovals represent damaged components; grey ovals represent subsequently disrupted processing.

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