On the organization of Semantic memory in the human brain

Neuroimaging evidence suggests that left hippocampal areas show an increase in activity during semantic memory tasks. Damage to areas involved in semantic memory result in various deficits, depending on the area and type of damage. It has been found that category specific impairments can occur where patients have different knowledge deficits for one semantic category over another, depending on location and type of damage. Category-specific impairments might indicate that knowledge may rely differentially upon sensory and motor properties encoded in separate areas .Category-specific impairments can involve cortical regions where living and nonliving things are represented and where feature and conceptual relationships are represented.
In this paper,
"Functional magnetic resonance imaging (fMRI) was used to examine the pattern of cortical activity during a picture naming task. Subjects (n=12) had to covertly name either animals or furniture items. Functional scanning was performed using a conventional 1.5-Tesla whole-body MRI system. Images obtained during naming the two categories were compared using a non-parametric test. The study revealed evidence for domain-specific lexical regions in left middle, right middle and inferior frontal areas, as well as in superior and middle temporal areas. The results corroborate neuropsychological data and demonstrate directly and non-invasively in human volunteers that semantic representations in frontal and temporal areas are, to some degree, localized and possibly implemented as multiple maps. A completely distributed storage of semantic information is rendered unlikely."
This goes in the favour of the idea that specific regions for episodic memory might just exist in the human brain and may not simply be an emergent property of semantic memory,as such.
I side with the idea that visual knowledge is most probably not a single attribute domain. Under this revised description of visual knowledge, in which visual knowledge itself is a distributed representation, a different set of predictions emerges: objects with multiple sources of knowledge about their appearance (e.g., vision, touch, actions) will be less susceptible to loss of any single source of visual knowledge .
Allport's cloud :
Damage to ventral visual processing regions, which represent only one source of information, will not necessarily cause an impairment to other representations of appearance for these things. This idea was present in Allport's (1985) description of attribute domains (he used the example “cloud”), but it was not included in many sensory-functional theories that, in effect, collapsed across all types of visual knowledge.
What I think:
1.Neuroimaging experiments need to be conducted on infants and lower animals,so as to understand better the organization of semantic memory.
2.Episodic memory,if present separately,alters the organization of semantic memory.Such evolutionarily favourable alterations must be passed on from generation to generation to obtain more advanced forms of semantic memory.
3.We dissect our thought process,when we listen to the word,say,"dog"When i think of a dog I think of a figure with drooping ears ,a set of sharp teeth and a wagging tongue.Also,some may imagine its complete body and think of a four legged entity.It is easy to see that these ideas are composed of semantic chunks:the semantics of "teeth,"tongue","four-legged ness" ,etc.But to a person,who was once badly bitten by a dog,the word "dog" would instill memories of that episode,for many,many years after the incident.In that person's brain the Allport cloud of the word dog,would have a major portion of itself lying in the tactile,than in the visual region.
4.The key to resolving all issues,is to find,how exactly,the notion of time,past and present,is encoded in the brain.
The usual references:
MITECS and wikipedia

Cognitive linguistics

Cognitive Linguistics arose in opposition to Chomsky's idea that language is in the mind alone, and do not relate to objects outside or the body.
Chomskian thought is more Cartesian,that is,it is more concerned with the inherent properties of the mind,whereas Cognitive linguists believe in the intricate relationship between the mind and body.While they do not outrightly deny the existence of an universal grammar,they say that even this universal grammar, if it exists,should have its roots in cognition.Some key ideas in Cognitive Linguistics are:

CONSTRUAL -
There are different ways of paraphrasing the same sentence,which often convey the same meaning,perhaps.But,we chose to use one of them given a situation.While generative grammarians would treat the different choices as compositional differences alone,cognitive linguists emphasise that there is a reason ,we choose one construal over another and this reason talks a lot about how our language is structured.
John gave the book to Mary vs John gave Mary the book - construes different and only one of the constructions seems natural in a given situation.

METAPHOR - It is not the exclusive domain of poets,it is the fundamental property of everyday language.It is about how we conceptualise one experience in terms of other(Lakoff)Eg:someone is very hot - extends the idea of heat to represent some aspect of the person.

PERSPECTIVE - The path falls steeply into the valley.The path climbs out of the valley.Both these sentences have this inherent notion of an observer,even though the actual position of the speaker is irrelevant.
Fundamentality of space:Spatial thoughts are often fundamental and extend to other domains via metaphor :This is best demonstrated in this way:We say "foot in the stirrup" but not "finger in the ring" because when we look at our palm,it seems to us that the finger is a 2-dimensional surface on which you have the projection of the ring.So we say "ring on the finger"

Another example is the containment metaphor - "In" I am in this classroom - indeed enclosed - so consistent with the base definition of containment

Bird is in the garden -here there is no definite three dimensional enclosure,but we do have the idea that the bird is hovering at a height close to the ground and we do have a fuzzy notion of a ceiling.I am in the class , We can look at it as belonging to an abstract set."words on the paper" (surface attachment)"words in the margin" (margin is a region,so containment)"up" points to vertical movement,so logically consistent to associate with increase in quantity -"prices shot up"."

"He ran up to meet him" ,is perhaps due to enlargement of retinal image on approach.
Some of these metaphors may be cultural - mole may be on the cheek(for English) or in the cheek(for other languages).It tells us about the cultural differences between the places where the different languages are spoken.But many of these metaphors are universal.Basically,beginning from the most basic dimensions like cognition to societal traits,everything influences language deeply.
Concept of schema:For example,the core meaning of out,where an entity(trajector ) is located outside a container or containing space(landmark)."The cat is out of the house."Here,cat is the trajector and house is the landmark.Such schema can be constructed for many locative prepositions.And these schema can be adjusted to explain pretty well,the varied usage of the same preposition in different contexts.

An interesting idea I came across is how lakoff argues even mathematics to be influenced by cognition.You may want to explore it.

Reference:

An Introduction to Cognitive Linguistics by David lee

On Categorization-Essay 5

Firstly,we look at how language influences characterization.For example,early work in color categorization is primarily concerned with establishing a correlation between a linguistic variable distinguishing colors (for example, how easy different colors are to name or how easy they are to communicate about) and a nonlinguistic cognitive variable over colors: memorability. Discovery of such a correlation was interpreted as support for the view that linguistic categorization can influence nonlinguistic perception/cognition.
I propose it is possible to construct an argument about how this idea supports the prototype theory:Having a word for something sharpens the boundaries of the category into which that thing falls.Let us elaborate this with an example:Consider the family of birds,when I decide to call members of that family a BIRD,what I am doing is I am reducing the entire family to a SINGLE four lettered entity called a BIRD.all birds except one,disappear to point to the word.This SINGLE entity should obviously invoke a single prototypical picture in our mind.Once a noun is had,the next step in language is to attach adjectives:say,BIG bird,SMALL bird,surely when we see sparrows and hummingbirds,we imagine them closer in categorical distances.Language,with its grammatical structure,its approach towards tenses and genders,plays a strong role in how we categorize a hitherto unseen object.But I also don't think it is a purely one way street.As language influences categorization and categorizations evolve and change,language(by which,I mean the nature of language in practice) should also evolve,else it will loose its relevance.The reason is language itself is a tool that does not work on the world but representations of it in our mind,and as categories of these representations change,language should also change.
An example of people going beyond similarity to produce their categorization judgements.An experiment was done in which an object needed to be categorized on the basis of the value of one dimension only.For example,one object was "an object three inches in diameter ",and pizza and quarter being the two associated categories.Although,the object was,if anything,closer to a quarter.Subjects judged it more likely to be a pizza than a quarter presumably because there is a constraint on the size of the quarter rather than a pizza.This kind of result comes because one object has a higher degree of variability than the other.These show that subjects consider variability as well as similarity while making a categorization.I think the existence of sub-categories within a category is also a pointer to the involvement of variability in the formation of categories.In the category of birds ,for example,we have birds of prey,water-birds,small birds,etc.The very formation of a category by looking at similarity often fundamentally means how that similarity is different from a more common similarity or a more fundamental similarity.I am not very clear but what I mean,that when we say,for example that "aeroplanes are vehicles that fly" we are inherently actually noticing the difference between the quality of flying of an aeroplane and the quality of rolling on road of a more common land vehicle.Sometimes ,I feel this is a very Hegelian dialectic -"that we form categorizations by noting similarities."
Categorization also emerges from the discreet nature of things around us,the ability of things to have their own unique qualities,a book for example has the quality of bookness,a chair has the quality of chairness.The tendency to categorize is innate even on an evolutionary level.Man's first reaction on seeing something unfamiliar,is to search for a feature that he is familiar with and for that moment categorize it within a known category.It is for this reason that we have such an exhaustive usage of similies in poetry,we have learnt to notice that sometimes we categorize things in a rather noteworthy manner,even if it is practically meaningless.I also believe very strongly that categorization is very closely linked to the way the world is arranged around us,and how much categorization actually helps in our survival.

References:

http://www.kmworld.com/Articles/Editorial/Feature/Why-categorize-9580.aspx
http://en.wikipedia.org/wiki/Categorization