Visual-acoustic mapping in posterior cortical atrophy: Evidence from a single case study

Abstract

University of Pennsylvania School of Medicine, Department of Neurology, Philadelphia, Pennsylvania, USAAccepted 6 July 2006IntroductionAnomiacanresultfromarangeofperceptualdeficits(e.g.,agnosia);cen-tral semantic degradation (e.g., dementia); impaired linguistic access (e.g.,aphasia);oracombinationofthesefactors(HodgesPMar-tin & Saffran, 1990). One unexplored possibility, however, is that anomiamayalsostemfromimpairedmappingofarbitraryphonologicalformsontoconcepts. Here, we investigated integrity of the phonology-semantics map-pingprocessinapatientwithposteriorcorticalatrophyassociatedwithAlz-heimer’s disease. We predicted that visual deficits should interfere with theability to link phonetic attributes to a novel object. We introduce anapproach, known as phonetic symbolism, to test this hypothesis.Some phonemic combinations have been found to be associated withideas such as magnitude of physical size, brightness, affection, and propernounsacrossmanyunrelatedlanguages(Nuckolls,1999;Ohala,1994;Sapir,1949). This effect, phonetic symbolism, is tested with a novel object and achoiceofpossiblenonwordnames.The‘‘best’’nameisselectedbymappingacoustic-phoneticpropertiesofaworddirectlyontophysicalfeaturesoftheobject (Ohala, 1994). For example, if one is forced to choose between twonames (pleek or ploke) for a tiny, bright yellow animal, they choose Pleekwithagreementfargreaterthanchance.Thischoiceismadethroughnon-ar-bitrary mapping of phonology directly onto an object’s visual attributes.Phonetic symbolism taps many crucial elements of word learning thatarenotdirectlyaccessiblethroughassessmentofknownobjectsandwords.Inordertocorrectlychoosethename,Pleek,apersonmustperceivesalientvisual attributes (e.g., brightness), process acoustic-phonetic features (e.g.,vowel height), and then complete a mapping of these characteristics. Theuse of novel stimuli (both words and objects), therefore, provides a uniqueway of examining potential deficits in word to object mapping.MethodCase descriptionAtrophy in the occipital and temporal visual areas and posterior por-tions of the parietal lobes causes patients with the visual-variant of Alzhei-mer’s disease (vAD) to have object recognition deficits and visuospatialproblems including optic apraxia and simultanagnosia. As vAD evolves,memory and language difficulties also become prevalent (Levine, Lee, F Ross, Graham, Stuart-Green, & Prins, 1996). CP is a 61-year-old, right-handed female diagnosed with vAD through examinationby a behavioral neurologist and consensus review using NINCDS-ADRDA criteria (McKhann et al., 1984).CP initially presented to the University of Pennsylvania (12/03) withsignificant visual-perceptual difficulties (profound difficulty copying thesimplest visual geometric designs) and also demonstrates mild semanticimpairment (Pyramids & Palm Trees Words 46/52). CP shows impairedconfrontation naming of pictures (Boston Naming Test: 3/15) and speechproduction significant for frequent circumlocutions, word-finding pausesand anomia. She was able to read and could appreciate the color butnot the form of visual stimuli. Structural MRI obtained in 2003 revealedleft ventral-occipital and parietal-occipital atrophy as well as mild rightparietal and inferior frontal atrophy Fig. 1.Experiment 1—Phonetic symbolismCP viewed 25 randomized images of novel objects (i.e., blobs, n = 10)and pseudoanimals (n = 15) presented via E-prime software on a laptopcomputer. Stimuli were manipulated by salience of visual features, includ-ing: brightness, physical size, angularity, roundness, motion, and loudness.Two monosyllabic (CVC or CVCC) nonwords appeared below eachimage. Nonwords varied by medial vowel, which maximally differed byplace and height (e.g., pleek–ploke). CP was instructed to ‘‘choose the bestname’’ for each image by signaling with a key-press. 13 healthy controlsdemonstrated high agreement on the target nonword selected as a namefor each item. Small, bright pseudoanimals were associated with high fre-quency/narrow vocal tract vowels; large, dark pseudoanimals with low fre-quency/wide vocal tract vowels; dull, dark blobs with back vowelsproduced with lip rounding; and sharp, bright blobs with high frequen-cy/narrow vocal tract vowels.ResultsCP did show a strong effect of phonetic symbolism for the manipula-tion of ‘‘roundness’’ collapsed across conditions. That is, CP reliably asso-ciated back, rounded vowels (e.g., ‘‘mome’’) with rounded objects andpseudoanimals (8/8) p < .004. Otherwise she did not associate phoneticfeatures with visual-perceptual attributes of novel objects andpseudoanimals.doi:10.1016/j.bandl.2006.06.075* Corresponding author. Fax: +1 215 349 8464.www.elsevier.com/locate/b&lBrain and Language 99 (2006) 8–219