I. Words in the Brain: Functional Webs (cont’d)

II. Right Hemisphere in Language Processing

Ling 411 – 14

Sequence

In language, sequence is very important• Word order• Order of phonological elements in syllables• Etc.

Also important in many non-linguistic areas• Dancing• Eating a meal

Can cortical columns handle sequences?

Simplified model of minicolumn I:Activation of neurons in a column

Thalamus

Other corticallocations

Subcorticallocations

IIIII

IV

VVI

Connections to neighboring columns not shown

Cell Types

Pyramidal

Spiny Stellate

Inhibitory

Lasting activation in minicolumn

Subcorticallocations

Connections to neighboring columns not shown

Cell Types

Pyramidal

Spiny Stellate

Inhibitory

Recurrent axon branches keep activation alive in the column –Until is is turned off by inhibitory cell

Notation for lasting activation

> Thick border for a node that stays active for a relatively long time > Thin border for a node

that stays active for a relatively short time

Recognizing items in sequence

This link stays active

a b

Node c is satisfied by activation from both a and b If satisfied it sends activation to output connections Node a keeps itself active for a whileSuppose that node b is activated after node a Then c will recognize the sequence ab

c

This node recognizes the sequence ab

Recognizing a syllable and its demisyllables

dim

di- -im

Cardinal node for dim

Functional subweb for dim

Auditory features of [di-]Auditory features of [-im]

Just labels

Local and distal connections

excitatory

inhibitory

Cardinal nodes vis-à-vis “grandmother nodes”

‘Grandmother node’: a node that responds to grandmother• i.e., a local representation for grandmother

The term ‘grandmother node’ usually refers to the naïve grandmother node• (To people who use the term)• Naïve grandmother node: a hypothetical node that would

recognize grandmother all by itself Alternative conception: the sophisticated grandmother node

• The cardinal node of a functional web

The sophisticated grandmother node

GRANDMOTHER has a distributed representation That distributed representation includes a cardinal node

• This cardinal node is a local representation Nodal specificity It represents a specific value: GRANDMOTHER

• Its receptive field is “grandmother” Its operation is supported by an entire functional web

• Other nodes in the web handle The details A range of diverse perceptual properties Variety

Arguments against ‘grandmother nodes’

They are directed against the naïve grandmother node• They usually assume that the local representation is

representing a concept (like ‘grandmother’) all by itself • i.e., Local representation without distributed

representation i.e., without a supporting web

Arguments against (naïve version of ) local representation

1. Recognizing new things and producing motor responses to new things are problematic on the local-coding theory

2. The patterns recognized visually by a human in a lifetime vastly outstrip the number of sensory processing neurons in the entire human nervous system

Churchland & SejnowskiThe Computational Brain MIT Press, 1992, p. 163

Arguments against (naïve version of ) local representation

1. Recognizing new things and producing motor responses to new things are problematic on the local-coding theory

This argument assumes that such a node recognizing grandmother all by itself. But it is the whole functional web that recognizes grandmother. Each part of this web naturally responds to a wide range of values, including novel values.

Arguments against (naïve version of ) local representation

2. The patterns recognized visually by a human in a lifetime vastly outstrip the number of sensory processing neurons in the entire human nervous system

Churchland & Sejnowski 1992:163

On the contrary, the web can accommodate recognition of multiple new exemplars without the need for recruiting additional nodes. Not a problem after all.New nodes are needed only for new learning.

Support for the cardinal node hypothesis

1. It follows from the properties of nodal specificity and hierarchy

• A hierarchy must have a highest level• The node at this level must have a specific function

2. It is needed for ignition of the whole web from activation of part of it

• For example, to activate the phonological representation from the visual

3. It is automatically recruited in learning anyway, according to the Hebbian learning hypothesis

4. Cardinal concept and phonology nodes are needed for the arbitrariness of the linguistic sign

Support for cardinal nodes - 2

The distributed network as a whole represents the concept (e.g. FORK)

The whole can evidently be ignited by any part of the functional web• From seeing a fork• From eating with a fork• Etc.

The cardinal node provides the coordinated

organization that makes such reactivation possible

Reactivating the functional web

When the cardinal node (the integrating node) is activated, it can activate the whole (distributed) functional web• Without it, how would that be possible?• E.g., activating conceptual and perceptual properties of

cat upon hearing the word cat• From phonological recognition to concepts• From visual image to phonological representation

Ignition of a functional word web from speech input (showing only major nodes)

V

MC

T

PRPA

PP

Ignition from visual input

V

MC

T

PRPA

PP

1

4

43

3 3

1

2

Ignition from tactile input

V

MC

T

PRPA

PP

1

4

43

3

3

1

2

Ignition from conceptual input

V

MC

T

PRPA

PP

1

3

32

2

2

1

2

Question

Also, I had a question about how functional webs activate when a node activates. Would it be possible to memorize or learn information that would be activated (remembered) later by repeating a word or other stimuli that is part of the neural web? This is something they do in spy movies, but I am unsure if it actually is possible.

Support for the cardinal node hypothesis – 3

It is automatically recruited in learning according to the Hebbian learning principle

Even if it weren’t there it would soon be recruited as a result of co-activation of its linked properties

This is the operating principle for building a functional web from bottom up• At each level, co-occurring properties will

activate a node at next higher level That newly activated node represents the

combination of those properties• This process continues up to top of hierarchy

Support for cardinal nodes – 4: The linguistic sign

Connection of conceptual to phonological representation Consider two possibilities

1. A cardinal node for the concept connected to a cardinal node for the phonological image

2. No cardinal nodes: multiple connections between concept representation and phonological image • supported by Pulvermüller (2002)

Pulvermüller’s hypothesis:No cardinal nodes

Friedemann Pulvermüller, The Neuroscience of Language, 2002

Phonological representation: a distributed representation in the perisylvian area

Meaning of a verb

Meaning of a visual object

Implications of possibility 2

No cardinal nodes: multiple connections between concept representation and phonological image

I.e., different parts of meaning connected to different parts of phonological image

Consider fork• Maybe /f-/ connects to the shape?• Maybe /-or-/ connects to the feeling of holding

a fork in the hand?• Maybe /-k/ connects to the knowledge that

fork is related to knife? Conclusion: Possibility 2 must be rejected

Pulvermüller’s hypothesis:No cardinal nodes

Friedemann Pulvermüller, The Neuroscience of Language, 2002

Phonological representation: a distributed representation in the perisylvian area

Meaning of a verb

Meaning of a visual object

Functional Webs acc. to Pulvermüller

1. Distributed representation of form and of meaning• This part is correct

2. Multiple connections between form and meaning• Runs counter to the linguistic evidence• Implication: parts of the phonological representation

connect to parts of the meaning• Example: walk - WALK

[w-] or [-k] for action with legs?

Properties of Cortical StructureApplied to Functional Webs

Property I: Intra-column uniformity of function• The nodes of functional webs are (implemented

as) cortical columns Property II: Cortical topography

• Every functional web is a two-dimensional array of columns

Property III: Nodal specificity• Every node of a functional web has a specific

function Property IV: Adjacency

• Adjacent nodes for related functions More closely related function, more closely adjacent

Property IV(b): A deduction from the adjacency property

The nodes in each area of a functional web• Constitute a subweb • Their function fits the portion of cortex in which

they are located For example,

• Phonological recognition in Wernicke’s area• Visual subweb in occipital and lower temporal lobe• Tactile subweb in parietal lobe

• Nodal specificity: Each node of a subweb also has a specific function within that of the subweb

Properties of Cortical StructureApplied to Functional Webs (cont’d)

Property V: Competition• Neighboring nodes are likely to be in competition

Typically they will be in different functional webs Property VI: Extension of II-V to larger columns

• Properties II-V apply also to maxicolumns and hypercolumns

Property VII: Hierarchy in functional webs• A functional web is hierarchically organized

Property VIII: Cardinal nodes Property IX: Reverberation

Property IX: Reverberation in functional webs

Reverberation among connections in an established web strengthens activation

Experimental verification:• The monkey experiment

Temporary lesion in part of the short-term memory web reduces activity in other part

• (considered last time)• Comparing words and pseudo-words

Pseudo-words: phonologically OK but no meaning

Property IX: Reverberation in functional websWords and pseudo-words (Pulverműller 2002)

Reverberation among connections in an established web strengthens activation

Experimental verification:• Compare words and pseudo-words• Real words show greater activation• “About one-half second after the onset of spoken

one-syllable words, high-frequency brain responses were significantly stronger compared to the same interval following pseudo-words.” (Pulverműller: 53)

Another word : pseudo-word experiment(Pulverműller 2002: 54-56)

Finnish• pakko ‘compulsion’• takko : a pseudo word• Same 2nd syllable• Measurement was done on response to -ko

Technique used for measuring: EEG, MEG Measurements used: MMN and MMNm

• MMN : mismatch negativity• MMNm: magnetic flux from mismatch negativity

(from MEG) Subjects were watching a silent movie

• I.e., not paying attention

Another word : pseudo-word experiment: Results(Pulverműller 2002: 54-56)

Measurements used: MMN and MMNm• (MMN : mismatch negativity)• Larger for –ko of real word• Strongest difference at 100-200 ms

after word-recognition point Word-recognition point: “the earliest point

in time when the information present in the acoustic input allows the subject to identify the word with some confidence”

• MEG showed that the activation was in left superior temporal lobe

Finnish ‘pakko’ experiment: discussion

[-ko] produces activation in either context, since it is a syllable occurring in Finnish• And in the area for phonological recognition

Stronger activation in pakko • pakko is an established word in Finnish• That means it has established connections to meaning• Established connections provide stronger activation• Indicates reverberation – strengthening of the

activation from other parts of the web For the pseudo-word, there are no other parts of a functional

web – only phonological information

Right Hemisphere in Language Processing

(What we are really talking about is non-dominant hemisphere – so it’s LH for RH-dominant people)

Major RH Linguistic Functions

Inference, Metaphor Coarse coding Music

Some findings w.r.t. RH speech perception

Vowel qualities Intonation Tones in tone languages

Possible bases for RH/LH difference

Higher ratio of white to gray matter in RH• Therefore, higher degree of connectivity in RH

Difference in dendritic branching Different density of interneurons Evoked potentials (EEG) are more diffuse over the

RH than over LH

Beeman 1998: 257

Anatomical differences between LH and RH

Geschwind & Levitsky (1968)• 100 brain specimens examined• Planum temporale

Larger in LH: 65% Larger in RH: 11% About the same, both sides: 24%

• Correlates with shape of Sylvian fissure Shorter horizontal extent in RH

Goodglass 1993:60

Some Experiments (described by Beeman 1998)

Words presented to rvf-LH or lvf-RH RH more active than LH

• Synonyms• Co-members of a category: table, bed • Polysemy: FOOT1 – FOOT2

• Metaphorically related connotations• Sustains multiple interpretations

LH about same as RH• Other associations: baby-cradle

LH more active than RH• Choose verb associated with noun

Patients with brain-damage

Some patients with LH damage• Can’t name fruits but can say that they are fruits

Patients with RH damage• Impaired comprehension of metaphorical statements• More difficulty producing words from a particular

semantic category than producing words beginning with a particular letter (258)

Imaging studies

When listening to spoken discourse, cerebral blood flow increases in• Wernicke’s area• Broca’s area• RH homologues of Wernicke’s and Broca’s areas

More cerebral blood flow in RH when subjects read sentences containing metaphors than literal sentences

Experiments on speech perception

Dichotic listening – normal subjects • Right ear (i.e. LH) advantage for distinctions of

Voicing Place of articulation

• Left hear (RH) advantage for Emotional tone of short sentences

• Sentences presented in which only intonation could be heard RH advantage for identifying sentence type

– declarative, question , or command

Experiments on speech perception

Split brain patients• They hear a consonant• Then written representations are presented• ‘Point to the one you heard’• rvf-LH exhibited strong advantage

Patients with right-brain damage

Posterior RH lesions result in deficits in interpreting emotional tone

Anterior RH lesions abolish the ability to control the production of speech intonation

Split-brain studies

Isolated RH has ability to read single words• But not as fast nor as accurate as LH• Ability declines with increasing word length• Lexical context does not assist letter identification

In Japanese subjects• RH is better at reading kanji than kana

Kanji: from Chinese characters Kana: syllabic writing system

• LH is better at reading kana

Musical abilities and the hemispheres

Pitch, melody, intensity, harmony, etc. in RH Rhythm in LH Absolute pitch (if present) in LH temporal plane Musicians’ ability to analyze chord structures in LH Appreciation of chord harmony in RH Discrimination of local melody cues more in LH Timbre discrimination in anterior right temporal lobe Melody recognition in anterior right temporal lobe

Evidence from results of brain lesions/surgery, from dichotic listening experiments, from Wada test experiments, and from imaging

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