Language

Linguistics meets the brain

Psycholinguistics attempts to describe a biological language network.• E.g., syntax theory: What kind of computer is our brain?• However, complex and abstract concepts are difficult to map to brain function.• E.g., phrase-structure rules, phonemes, function vs. content words, change of state verbs

In animals

As far as I am aware, the neural basis for the remarkable behavior of bees also remains a mystery. This behavior includes what appear to be […] some of the few known analogues to distinctive properties of human language, notably […] communication about objects not in the sensory field. The prospects for vastly more complex organisms seem considerably more remote.” (Chomsky, 2000)(a bee has ca. 1 million neurons)

For example, in the case of the roundworm (Caenorhabditis elegans), we know the genome, the cell types, and the connectome—every cell and its connections. Despite this wealth of knowledge, our understanding of how all this structure maps onto the worm’s behavior remains frustratingly incomplete.” (Krakauer et al., 2017)(a roundworm has 302 neurons)

Broca’s aphasia (non-fluent aphassia)

Leborgne had difficulties speaking after stroke.• Output: “tan”, and swearing (“Sacré nom de Dieu.”• Language comprehension appeared intact.• Motor control of face, mouth and tongue not compromised.• Broca: Lesion affected speech control.• Lesion damaged pars opercularis and pars triangularis of the LIFG (“Broca’s area”)

Wernicke's aphasia (fluent aphasia)

Patients showed impaired comprehension and loss of meaningful speech (paraphasia).• Articulation normal.• Grammar mostly normal.

Ludwig Lichtheim and connections

Proposal: Lesion to Broca's area, Wernicke's area or the connection between areas account for language deficits.• Lichtheim's (1885) House model:‘The reflex arc consists in an afferent branch aA, which transmits the acoustic impressions to A; and an efferent branch Mm, which conducts the impulses from M to the organs of speech; and is completed by the commissure binding together A and M. When intelligence of the imitated sounds is superimposed, a connection is established between the auditory centre A, and the part where concepts are elaborated, B.’

A is wernicke, M is broca and motor,

Conduction aphasia

Rare aphasia.• Good comprehension.• Fluent, paraphasic production.• Impaired language repetition.• Assumption: Lesion to fibers connecting A and M.

The belief that due to deficit you only say the most necessary as you do not have the resourcesto say everything

The Arcuate Fasciculus

Fibers that connect wernicke and Brocas areas

Dorsal fibers connecting A and M.

Wernicke-Geschwind model

Broca's area: Language production.• Wernicke's area: Language comprehension.• Arcuate Fasciculus connecting the areas.• Angular gyrus: reading (damage can result in alexia)

Challenges to the Wernicke-Geschwind model

We don’t really need grammar to understand language

Grammatical comprehension impairment

How can comprehension appear normal despite grammatical comprehension impairment?• Sentence comprehension does not always require grammatical comprehension:• The boy kicks the ball• boy, kick, ball• kick, ball, boy• World knowledge helps.b tense, but

Still missing information about verb tense but we still understand

Semantically reversible sentences require interpretation of sentence structure:• The horse kicks the girl.• The girl kicks the horse.• The girl is kicked by the horse.• The horse is kicked by the girl.• People with aphasia can fail to match reversible sentences with the correct picture.• Most prominent in Broca’s aphasia.• Agrammatism affecting production and comprehension.

Problems with Broca’s area

Voxel-based lesion-symptom mapping on 101 aphasic stroke survivors (Bates et al., 2003).• Lesions within the insula and deep parietal white matter had the largest impact on speech production and fluency.• Areas also associated with comprehension.• Anterior insula also related to fluency (Blank et al., 2002).

Problems with Wernicke’s area

Voxel-based lesion-symptom mapping on 101 aphasic stroke survivors (Bates et al., 2003).• Injury to middle temporal gyrus had the largest effect on auditory comprehension.• Another VBLS mapping study (Schwartz et al., 2009) associated anterior temporal damage with semantic naming errors.

One alternative: The declarative/procedural model

Distinction between lexicon and grammar more important than between comprehension and production.• Remember: Distinction between declarative (conscious) and procedural (non-conscious) memory.• Ullman (2001) mapped the lexicon to declarative memory and grammar to procedural memory.• Declarative memory: temporal and temporoparietal regions.• Procedural memory: Basal ganglia and frontal cortex.

One application: verb inflection

Second application

Evidence from aphasia:• In some studies on Broca’s aphasia, performance on irregular forms is better than on regular forms (e.g.Penke et al., 1999).• However, a meta-analysis of 75 patients with Broca’saphasia found much heterogeneity and no clear dissociation overall (Faroqi-Shah, 2007).• Difficulties with regular tense production and comprehension found in Broca’s and Wernicke’s aphasia (Jonkers et al., 2009).• Results from aphasia may challenge the procedural/declarative model.

Another alternative: Memory, Unification, Control

No widely established alternative, but MUC (Memory, Unification, Control) represents current trends (Hagoort, 2013).• Distinction less between production and comprehension less important than between storage and combination.

Memory unification control

Memory: word forms and meaning, grammatical processes• posterior temporal cortex and angular gyrus in parietal cortex• Unification: phonological, semantic, grammatical• Broca’s and surrounding areas• Control: language in social interaction, e.g. relevance of information, appropirateness• Frontal areas and parts of parietal cortex• Model may be more compatible with aphasic data on regular and irregular forms.

MUC] allocates the role of unification to the LIFG. Unification is defined as combining linguistic elements into larger units and it is recognized that unification operations occur in parallel in semantic, syntactic, and phonological domains. Although the author does not explicitly talk about morphology, it can be seen how both regulars and irregulars involve the same semantic and syntactic unification operations, differing only in morphological unification. Therefore LIFG lesions would impair both regular and irregular verb “unification” operations (Faroqi-Shah, 2007).

Holistic vs. analytic language processing

Islands of fluency and grammaticality in Broca’saphasia, e.g. “It’s alright”, “I can’t say it”.• Sometimes quite complex: “I don’t know what it is.” (Bruns et al., 2019)• How is this possible, if grammar is impaired?• Holistic (dictionary.com)“characterized by the belief that the parts of are intimately interconnected and explicable only by reference to the whole”

There is more than just words and rules.• Analytic processing via words and rules accounts for novel expressions, e.g.• Common language may be processed as one holistic unit, e.g. “I don’t know” (perhaps the most frequent sentence in English).

Frequency is one of the determining factors, it is easier to remember as a unit fir the brain