Behavioral Results

Brocas Area and the Language InstinctBy Peter Dang and Kyle Dennison

IntroductionAbility to acquire language is a unique and essential human trait

Chomskys Universal GrammarThe human brain contains a limited set of rules for organizing languageAssumption that all languages have a common structural basisPurpose of the StudyPurpose: To investigate the system underlying the acquisition of new linguistic competence based on Chomskys UG

Alternative View: The human mind is a general learning tool without specialized structuresMethodsTwo fMRI experimentsBoth consisted of native German speakersDifference was whether participants learned Japanese or Italian

Subjects were to learn 3 grammatical rules in foreign language and 3 artificial rules of an unreal languageMethods (Cont)Prior to the experiment, participants were given a list of words to memorize

Avoid confounding syntactic rule acquisition with word learning

Recall ability was tested over wordsfMRI TrialsSubjects learned real and unreal grammatical rules during pauses of 3 minutes between sessions in the form of slidesSubjects read 6 sentences in real and unreal languages and judged their syntactic correctnessCorrect Left middle fingerIncorrect Left index finger

Grammatical Rule ExamplesNull-subject parameterGerman: I eat the pearItalian: Eat the pear

Subordinate constructionGerman: Pia says that Paolo the pear eatsItalian: Pia says that Paolo eats the pearUnreal Grammatical RulesNegative ConstructionPaolo eats the no pear

Interrogative ConstructionPear the eats Paolo

Relevant Brain Regions

Behavioral ResultsEight subjects from each experiment were analyzed:

In judging the syntactical correctness of sentences the subjects achieved the same percent correct by the end of the experiment.Real Italian: 97 4.1 %Unreal Italian: 91.6 10%Real Japanese: 97 3.2%Unreal Japanese: 94 4.68%Behavioral Results ContinuedThe increase in performance between the acquisition of real vs. unreal rules was not significantly different.

T7 = 0.1, P = 0.57 in the first fMRI experiment

T7 = 0.5, P = 0.32 in the second fMRI experimentFigure 1a

Figure 1 Behavioral measurements. (a) Performance (mean % correct) injudging the syntactical correctness of the sentences presented in each of thefive fMRI sessions per learning task (data averaged across subjects).Performance showed an improvement across sessions during the learningtasks. Performance increase was not significantly difference between theacquisition of real versus unreal Italian (left) or Japanese (right) grammaticalrules.Behavioral Results: Reaction Time Over the course of the sessions subjects responded faster (reduced RT) and improved in accuracy.

There were four of these experiments: Real vs. Unreal Italian and Real vs. Unreal Japanese.

In every reaction time experiment the faster responses were significant:

T7 = 0.79, P < 0.0001Reaction Time Results ContinuedSubjects were able to make faster grammatical judgments in the real learning tasks than in the unreal learning tasks (Both Italian and Japanese).

Real vs. Unreal Italian: T7 = 0.79, P < 0.0001

Real vs. Unreal Japanese: T7 = 1.9, P < 0.03

These results are significant.Figure 1b

Figure 1 Behavioral measurements. (b) Mean reaction times (RT) for the correct syntactical judgment of the presented sentences in each of five fMRI sessions per task. Subjects showed a significant RT reduction (P < 0.0001) across sessions in all grammatical rules learning tasks. Reaction times were faster during the grammatical learning tasks (either Italian or Japanese) than during the artificial learning tasks (P < 0.03).Functional Imaging ResultsThere were two conditions:Looking at a black screen (the baseline task)

Judging grammatical correctness of sentences (classification task)

With the condition of judging grammatical correctness fMRI data showed activation in:Anterior Cingulate

Occipital Cortex

Cerebellum

Inferior and middle temporal gyrus

Prefrontal parietal

P < 0.05 and corrected for multiple comparisonsfMRI Results ContinuedfMRI measured blood-oxygen level dependent (BOLD) signal

A random effects model was used to identify the activation pattern specific to the interaction between the change in BOLD signal and type of rule learning (real or unreal) reflected by accuracy of performance.

No specific pattern of brain activation was found for unreal grammatical acquisition (Italian or Japanese).

There was an interaction between real and unreal grammatical acquisition in Brocas Area (pars triangularis of the left inferior frontal gyrus).

In this area the increase in BOLD signal was correlated with the increase in accuracy during the acquisition of natural rules for Japanese and Italian.Figure 2

Figure 2 Result of the interaction between performance and type of rule learning (real versus unreal Italian). Left, the activation specific to real language acquisition resulting from the random effects analysis is displayed on selected slices of the MRI template available in SPM99. The threshold was set at P < 0.05 (corrected for multiple comparisons). Right, plots of changes in BOLD (blood oxygen-level dependent) signal in the left inferior frontal gyrus (Talairach coordinates x, y, z: 45, 21, 6) for the five sessions containing real grammatical rule trials and the five sessions with unreal grammatical rule trials are shown as a function of accuracy within sessions. The distances between individual subjects peak voxel and the peak voxel derived from the group analysis using a random model were 28, 23, 3, 24, 13, 11, 23 and 15 mm, respectively, for subjects 18.Figure 2 Images

Figure 4

Figure 4 Results of the interaction betweenperformance and type of rule learning (real Italian versus unreal Italian in yellow; real versus unreal Japanese in red) resulting from the random effects analysis are shown on selected slices of the T1 template, thresholded at P < 0.001 (uncorrected) for visualization. Right, plots of individual changes in BOLD signal in the left inferior frontal gyrus during the acquisition of grammatical rules of either real or unreal Japanese are shown as a function of accuracy within sessions The distances between individual subjects peak voxel and the peak voxel derived from the group analysis using a random model were 12, 21, 25, 9, 9, 9, 6 and 11 mm,respectively, for subjects 18.Figure 4 Images

fMRI Results: Brocas AreaThe correlation coefficient between parameter estimates in Brocas Area and the accuracy of performance showed:

A significant positive correlation between BOLD signal and accuracy in the real grammatical task.

Italian experiment: r = + 0.66, P < 0.001

Japanese Experiment: r = + 0.47, P < 0.001

A significant negative correlation between parameter estimates (BOLD signal) and learning unreal rules.

Italian experiment: r = - 0.50, P < 0.001

Japanese experiment: r = - 0.32, P = 0.021

fMRI Results Not in Brocas AreaThere was a significant increase in BOLD signal in 2 parts of the right inferior frontal gyrus related to better performance (accuracy).

This positive correlation between BOLD signal and accuracy occurred for both the real (Italian and Japanese) and unreal (Italian and Japanese) tasks.

Real Italian r = .37, P = .008; Real Japanese r = .21, P = .009

Unreal Italian r = .33, P = .01; Unreal Japanese r = .040, P = .004

There was also activation in the left lingual gyrus

The Japanese study showed further activation in the:Left cingulate, Right Insula, Right supramarginal gyrus, and Left cerebellumFigure 3

Figure 5

Discussion: Right Inferior Frontal GyrusAdults acquire language by learning explicitly about grammar.

The inferior frontal gyrus is part of a neuronal system that deals with episodic memory retrieval.

Its generally accepted that the job of the right inferior frontal gyrus in learning real and unreal rules is to monitor information independently of its character.

It retrieves either hierarchical or linear information from episodic memory when making a response.

Explicit retrieval of information does not seem to be enough to acquire proficiency in a new language.Discussion: Brocas AreaThis study presents neurophysiological evidence that learning UG based and Non-UG based languages involves different brain systems.Brocas Area plays a significant part in learning real language rules.

Because languages from different families were used general statements can be made about acquiring language.

The study points to a universal syntactic specialization among real languages because activation of Brocas area occurred regardless of language of the subjects.

This study combined with previous research leads the authors to think that this region is specialized for acquiring and processing hierarchical structures (common character of every known grammar)

Additional support is provided by the negative correlation between BOLD signal and learning unreal grammatical rules.Other Evidence Suggesting Brocas ImportanceMembers of the KE family are prone to dysphasia (difficulty understanding/speaking language, either written or spoken).

There are structural and functional abnormalities in the left prefrontal cortex, which includes Brocas area.

Problems with the FOXP2 gene are the likely cause of KE familys disorders

This is consistent with the observation that language impairments can run in families and are more concordant in identical than fraternal twins.

This shows that genetic material can influence language ability.Evolution and Brocas AreaThe target of selection in humans appears to be the FOXP2 gene.

Results seem to support a common origin for human speech and possibly some communication in non-human primates.

Chimpanzees and gorillas learn words, but they dont have the same syntax abilities as humans nor are their sign motions as well defined.

Monkeys show left hemisphere asymmetry similar to humans, but the left inferior frontal lobe has less cellular density and is less differentiated

This study in particular demonstrates that the left inferior frontal gyrus is centrally involved in acquiring new languages based on UG.

The authors speculate that the complexities of Brocas area may be what makes us different from the other primates.