Cognitive neuroscience

The study of neural mechanisms underlying cognition, using converging behavioral, physiological, imaging, computational and intervention evidence. A location associated with a task is not by itself an explanation of the task's computation.

Resources or strategies allowing performance to remain effective despite brain changes. A later clinical symptom onset can be compatible with reserve without implying a lower disease incidence or less underlying pathology.

Representations of the body used for sensation, action and judgments about body parts or ownership. These functions can dissociate, so the term need not denote one unified map.

A disturbed belief about ownership of a body part, for example attributing one’s limb to another person. This goes beyond inaccurate localization of a visual target.

Impaired acknowledgment or recognition of part of one’s body. It is not interchangeable with every form of visual neglect.

A pattern of neural activity that carries task-relevant information under a specified decoding or explanatory model. Anatomical co-location, similar mean activation and a shared representational code are different claims.

A representation whose relevant information is independent of a particular sensory or output modality. Shared mean activation across modalities is weaker evidence than generalisation of information about the represented content, with confounded stimuli and responses controlled.

Conceptual information accessible through different forms such as words, signs and pictures. Shared conceptual content can coexist with modality-specific input and output pathways; an anatomical overlap alone does not establish identical neural codes.

Consider two response vectors $x=(3,1,3,1)$ and $y=(3,3,1,1)$ over the same four measured locations, relative to a zero baseline. Both are positive everywhere and have mean two. Their centered vectors $x_c=(1,-1,1,-1)$ and $y_c=(1,1,-1,-1)$ satisfy $x_c\cdot y_c=0$. Hence identical positive regional means can accompany orthogonal patterns. This counterexample shows why overlapping regional activation does not imply a shared neural representation. It does not assert that real neural codes are necessarily orthogonal or that unsuccessful decoding proves their independence.

The relationship between a neural activity pattern and information represented by that pattern. Testing a shared neural code requires more than activation in the same anatomical territory: the informative pattern or mapping must generalize under an appropriate comparison.

Processes supporting language comprehension and production. Neural models must distinguish the transformations required by a task from correlated memory, decision and motor demands.

Differences in neural responses associated with literacy experience. Comparisons including adult learners constrain purely childhood explanations while remaining vulnerable to nonrandom educational histories.^[ref]

Identification of a word form under a specified input modality. Accuracy, speed and access to meaning are distinguishable measurements.

How often a word occurs in a defined language sample or learning history. Corpus frequency and an individual child's actual exposure need not coincide.

Identification of printed word forms. Familiar-word accuracy, unfamiliar-word decoding, fluent access and semantic interpretation should not be treated as interchangeable outcomes.

Acquisition of information about written forms and their relations. Retention of a particular spelling and generalisation to untrained combinations are different outcomes.

Variation in surrounding letters while a target mapping remains stable. A first-grade training experiment found transfer benefits from varied consonants around vowel mappings, motivating tests of how example distributions support abstraction.^[ref]

Participants learn controlled written forms, pronunciations and sometimes meanings, followed by trained-item and transfer tests. Manipulating frequency and consistency can test sensitivity to input structure without uniquely identifying a learning algorithm.^[ref]

The proposal that phonological recoding of unfamiliar written forms creates opportunities to acquire word-specific orthographic representations. Delayed discrimination from homophonic alternatives tests more than immediate pronunciation.^[ref]

Efficient and appropriately coordinated reading, assessed through specified accuracy, speed and connected-text demands. Accurate isolated-word performance need not establish fluent passage reading.

Accessing a lexical item for comprehension or production. Naming additionally requires conceptual access and an output plan, so impaired naming need not identify a single representational deficit.

Acquired impairment of language following brain injury or disease. A diagnostic label can encompass multiple deficits and lesion patterns; behavioral components must be measured rather than inferred solely from the label.

Improvement in language function following acquired impairment. Residual tissue, network reorganisation, task practice and rehabilitation can contribute; recovery should be assessed across useful functions and time.

A clinical syndrome with progressive language impairment as the principal initial problem. Detailed profiles distinguish loss of word meaning, motor speech difficulty, agrammatism and phonological-memory demands; a syndrome label is not a unique anatomical lesion or molecular pathology.

A PPA pattern involving word-finding pauses and impaired repetition, with phonological-memory limitations often important. Sentence length and syntactic complexity should be varied independently when testing comprehension.

A PPA pattern prominently affecting word and conceptual meaning. Failure to understand a sentence can arise from missing word knowledge even if some grammatical operations remain available.

A PPA pattern characterised by effortful or agrammatic language, often with apraxia of speech. Motor speech and syntactic comprehension should be measured separately; neither is established merely by slow output.

A disproportionate naming difficulty for visually presented objects despite evidence of recognition. Nonverbal knowledge and naming through other input routes help distinguish it from visual agnosia.

A pattern of impaired semantic processing often investigated after stroke, in which regulating the use of knowledge can be especially difficult. The label does not imply that every patient has the same brain lesion or precisely the same mechanism.

Difficulty retrieving names. A naming failure can reflect lexical access, phonological output or degraded semantic knowledge, so naming alone does not diagnose failed object recognition.

An unintended substitution or alteration in speech, involving sounds or words. Fluent output can contain many such errors and therefore need not convey accurate information.

An aphasic presentation dominated by difficulty understanding language. This descriptive dimension does not identify one necessary brain lesion or exclude production deficits.

A fluent aphasic syndrome in which comprehension, repetition and informative speech can all be impaired. Acoustic–phonological analysis, semantic representations and semantic control must be distinguished; receptive difficulty does not imply preserved production.^[ref]

An aphasic pattern featuring disproportionately impaired repetition relative to some other language abilities. It can involve dorsal temporoparietal network dysfunction and is not proof of one isolated tract lesion in every case.

Temporal and temporofrontal systems supporting transformations from speech signals toward lexical and conceptual interpretation. Models differ on the precise anatomy and levels of representation included; bilateral speech analysis is compatible with stronger lateralization of some higher-level operations.

A family of dorsal connections supporting transformations between auditory/phonological information and frontal articulatory systems. In influential dual-stream models it is strongly left-biased, while remaining interactive with other systems rather than an isolated serial cable.

A task in which a person selects a picture corresponding to a sentence. Reversing thematic roles while preserving the pictured participants can test syntactic interpretation, but visual analysis and response selection remain additional requirements.

A disorder of speech fluency involving disruptions such as repetitions, prolongations or blocks. Proposed timing and motor-control mechanisms must account for variability across conditions and development; brain differences measured after onset can include consequences or compensation.

Impaired planning or programming of the coordinated movements needed for speech, distinguished from a primary muscle weakness or a deficit in grammatical knowledge. It can arise in developmental or acquired conditions.

A developmental motor-speech condition affecting the planning or programming of speech movements. Language skills and nonverbal cognition require separate assessment rather than being inferred from the severity of speech output difficulty.

A disproportionate difficulty recognizing spoken language despite better access through other routes. Hearing, phonological discrimination, reading and nonverbal semantic performance must be compared before attributing failure to a speech-input mechanism.

Inferring a particular mental process from a neural response associated with it. The inference is weak when the same response occurs during many other processes; task contrasts, functional selectivity and intervention evidence can constrain alternatives.