Table 6. The 10 clusters produced by the NCuts algorithm performed on the nearest-neighbor graph from year 2001–2006 (see Materials and Methods).

Cluster ID	Size of Cluster	Topic Label	Most Frequently Used Words
1	16729	Substance Abuse & Addiction	BEHAVIOR, LEVEL, COCAINE, DOSE, DRUG, INJECT, TREATMENT
2	22647	Cellular Neuroscience	SYNAPTIC, PROTEIN, CURRENT, CHANNEL, POTENTIAL, DENDRITIC, SUBUNIT
3	492	Behavior of Song Birds	SONG, HVC, BIRD, VOCAL, AUDITORY, FINCH, SING
4	7210	Pain & Trauma	SPINAL, PAIN, RECEPTOR, MUSCLE, INJURIES, DORSAL, MORPHINE
5	19988	Proteins, Gene Expression & Molecular Biology	CELL, NEURON, EXPRESS, ACTIVE, BRAIN, GENE, RECEPTOR
6	3609	Alzheimer's Disease	AD, AMYLOID, TAU, ALZHEIMER, PEPTIDE, PLAQUE, ABETA
7	736	Education & Informatics	STUDENT, DATA, LEARN, PROGRAM, MODEL, SCHOOL, INFORMATICS
8	794	Biological Rhythms	CIRCADIAN, SCN, LIGHT, RHYTHM, PHASE, CLOCK, CYCLE
9	14192	Visual & Motor Systems	RESPONSE, TASK, VISUAL, SUBJECT, CORTEX, MOVEMENT, STIMULUS
10	1146	Sleep	SLEEP, WAKE, REM, EEG, DEPRIVATION, PERIOD, WAVE

Abbreviations: HVC = “High Vocal Center”; AD = “Alzheimer's Disease”; REM = “Rapid Eye Movement”; SCN = Suprachiasmatic Nucleus”.

The third column of the table shows the subjective topic label assigned by domain experts to each cluster. The last column shows the 7 most distinguishing words found in the 20 most frequently used words in each cluster.