NBIO 220:  Central Mechanisms in Visual Perception


Instructors:  Bill Newsome (bill@monkeybiz.stanford.edu)
& Tirin Moore (tirin @stanford.edu)
Location: Clark Center, Lounge, First Floor West, Rm. 110
Days and Times: Monday 11:00 - 1:00 pm and Thursday 10:00am - 12:00 noon

*Changes have been made to the schedule of class times due to the NIS Conference and Memorial Day*

Student project, background research, 33%
Student project, class project, class presentation, 33%

Participation in class discussions of original research papers, 33%

Week 1: Thursday, March 31: Organizational Meeting & Lecture. Two hours.

Newsome: "The cortical visual system of primates"

Background Presentation


Week 2 (April 4): Introductory lectures, continued. Each two hours.

April 4: Moore: "The oculomotor system: physiology and psychophysics of eye movements"
April 7: Moore: "The oculomotor system: physiology and psychophysics of eye movements", Part 2.

Background Presentation

April 4th - Background Reading for Lecture

Kandel, Schwartz, Jessell, The Control of Gaze, Chapter 39.
Schall JD (1995). Visuomotor areas of the frontal lobe. In: Cerebral Cortex, Vol. 12: Extrastriate Cortex in Primates, pp. 527-638.

April 7th - Background Reading for Lecture

Kandel, Schwartz, Jessell, Voluntary Movement, Chapter 38.
Snyder LH, Batista AP, Andersen RA. Intention-related activity in the posterior parietal cortex. A Review, Vision Research 40:1433-1441, 2000.


Week 3 (April 11): Prefrontal Cortex: working memory

Background Presentation

Required Reading:

Rao SC, Rainer G, Miller EK. Integration of what and where in the primate prefrontal cortex. Science 276:821-824, 1997. pdf

Tomita H, Ohbayashi M, Nakahara K, Hasegawa I, Miyashita Y. Top-down signal from prefrontal cortex in executive control of memory retrieval. Nature 401:699-703, 1999. pdf

Wang M, Vijayraghaven S, Goldman-Rakic, PS. Selective D2 receptor actions on the functional circuitry of working memory. Science 303:853-6, 2004. pdf


Week 4 (April 18): Prefrontal Cortex: executive function

Background Presentation

Required Reading:

Stuphorn V, Taylor TL, Schall JD. Performance monitoring by the supplementary eye field. Nature 208:857, 2000. pdf (For Monday, read first)

Ito S, Stuphorn V, Brown JW, Schall JD. Performance monitoring by the anterior cingulate cortex during saccade countermanding. Science 302:120-122, 2003. pdf (For Monday, read second)

Wallis JD, Anderson KC, Miller EK. Single neurons in prefrontal cortex encode abstract rules. Nature 411:953-956, 2001. pdf


Week 5 (April 25): Visual Attention 1: Target selection for eye movement

Background Presentation

Required Reading:

Bichot NP, Schall JD. Effects of similarity and history on neural mechanisms of visual selection. Nat. Neurosci. 26:549-54, 1999. pdf

McPeek RM, Keller EL. Deficits in saccade target selection after inactivation of superior colliculus. Nat. Neurosci. 7:757-63, 2004. pdf

Sheinberg DL, Logothetis NK. Noticing familiar objects in real world scenes: the role of temporal cortical neurons in natural vision. J. Neurosci. 21:1340-50, 2001. pdf


Week 6 (May 2): Visual Attention 2: covert attention

Background Presentation

Required Reading:

Cavanaugh J, Wurtz RH. Subcortical modulation of attention counters change blindness. J. Neurosci.24:11236-43, 2004. pdf

Moore T, Armstrong KM. Selective gating of visual signals by microstimulation of frontal cortex. Nature 421:370-3, 2003. pdf

Bisley JW, Goldberg ME. Neuronal activity in the lateral intraparietal area and spatial attention. Science 299:81-86, 2003. pdf


*Changes have been made to the schedule of class times due to the NIS Conference and Memorial Day*

Week 7 (Thursday, May 12th and Friday, May 13th at 10:00 am): Decision-making: sensory mechanisms

Background Presentation

Required Reading:

Gold JI, Shadlen MN. Neural computations that underlie decisions about sensory stimuli. Trends in Cog. Sci. 5:10-16, 2001. pdf

Roitman JD, Shadlen MN. Response of neurons in the lateral intraparietal area during a combined visual discrimination reaction time task. J. Neurosci. 22:9475-89, 2002. pdf

Wang, XJ. Probabilistic decision-making by slow reverberation in cortical circuits. Neuron 36:955-968, 2002. pdf


Week 8 (May 16): Decision-making: reward assessment

Background Presentation (on May 16th)

Required Reading:

Barraclough DJ, Conroy ML, Lee D. Prefrontal cortex and decision-making in a mixed-strategy game. Nature Neurosci. 7:404, 2004. pdf

Dorris MC, Glimcher PW. Activity in posterior parietal cortex is correlated with the relative subjective desirability of action. Neuron 44:365, 2004. pdf

Sugrue, LP, Corrado GS, Newsome, WT. Matching behavior and the encoding of value in parietal cortex. Science 304:1782-1787, 2004. pdf
Supporting material pdf


Week 9 (May 23): Sensorimotor Integration: coordinate transformations

Background Presentation

Required Reading:

Duhamel JR, Bremmer F, Ben Hamed S, Graf W. Spatial invariance of visual receptive fields in parietal cortex neurons. Nature 389:845-848, 1997. pdf

Graziano MSA, Yap GS, Gross CF. Coding of visual space by premotor neurons. Science 266:1054-1057, 1994. pdf

Pouget A, Deneve S, Duhamel J-R. A computational perspective on the neural basis of multisensory spatial representations. Nature Reviews Neuroscience, 741, 2002. pdf


Week 10 (June 2nd; June 6th at Bill's place): Perception, Working Memory and Decision-making in the Somatosensory System.

Background Presentation

Required Reading:

Machens CK, Romo R, Brody CD. Flexible control of mutual inhibition dynamics: an integrated neural model of two-interval discrimination. Science 307:1121-1124, 2005. pdf

Romo R, Brody CD, Hernandez A, Lemus L. Neuronal correlates of parametric working memory in the prefrontal cortex. Nature 399:470-473, 1999. pdf

Romo R, Hernandez A, Zainos A, Brody CD, Lemus L. Sensing without touching: psychophysical performance based on cortical microstimulation. Neuron 26:273-278, 2000. pdf


Background Reading:

Week 3 (April 11):

Chafee MV, Goldman-Rakic PS. Inactivation of parietal and prefrontal cortex reveals interdependence of neural activity during memory guided saccades. J. Neurophysiol. 83:1550-66, 2002.

Funahashi S, Bruce CJ, Goldman-Rakic PS. Mnemonic coding of visual space in the monkey's dorsolateral prefrontal cortex. J. Neurophysiol. 61:331-49, 1989.

Funahashi S, Bruce CJ, Goldman-Rakic PS. Dorsolateral prefrontal lesions and oculomotor delayed-response performance: evidence for mnemonic "scotomas". J. Neurosci. 13:1479-97, 1993.

Funahashi S, Bruce CJ, Goldman-Rakic PS. Neuronal activity related to saccadic eye movements in the monkey's dorsolateral prefrontal cortex. J. Neurophysiol. 65:1464-83, 1991.

Fuster JM. Unit activity in prefrontal cortex during delayed-response performance: neuronal correlates of transient memory. J. Neurophysiol. 36:61-78, 1973.

Goldman-Rakic PS. Cellular basis of working memory. Neuron 14:477-85, 1995.

Miller EK, Erickson CA, Desimone R. Neural mechanisms of visual working memory in prefrontal cortex of the macaque. J. Neurosci. 16:5154-5167, 1996.

Rainer G, Rao SC, Miller EK. Prospective coding for objects in primate prefrontal cortex. J. Neurosci. 19:5493-505, 1999.

Rao SC, Rainer G, Miller EK. Integration of What and Where in the primate prefrontal cortex. Science 276:821-824, 1997.

Sawaguchi T, Goldman-Rakic PS. D1 dopamine receptors in prefrontal cortex: involvement in working memory. Science 251:947-50, 1991.

Sawaguchi T, Matsumura M, Kubota K. Effects of dopamine antagonists on neuronal activity related to a delayed response task in monkey prefrontal cortex. J. Neurophysiol. 63:1401-12, 1990.

Selemon LD, Goldman-Rakic PS. Common cortical and subcortical targets of the dorsolateral prefrontal and posterior parietal cortices in the rhesus monkey: evidence for a distributed neural network subserving spatially guided behavior. J. Neurosci. 8:4049-68, 1988.

Williams GV, Goldman-Rakic PS. Modulation of memory fields by dopamine D1 receptors in prefrontal cortex. Nature 376:572-5, 1995.

Week 4 (April 18):

Botvinick M, Braver TS, Barch DM, Carter CS, Cohen JD. Conflict monitoring and cognitive control. Psychol. Rev. 108:624, 2001.

Bunge SA, Kahn I, Wallis JD, Miller EK, Wagner AD. Neural circuits subserving the retrieval and maintenance of abstract rules. J. Neurophysiol. 90:3419-28, 2003.

Duncan J, Emslie H, Williams P, Johnson R, Freer C. Intelligence and the frontal lobe: The organization of goal-directed behavior. Cogn. Psychol. 30:257-303, 1996.

Holroyd, CB, Coles MGH. The neural basis of human error processing: reinforcement learning, dopamine, and the error-related negativity. Psychol. Rev. 109:679, 2002.

Miller EK. The prefrontal cortex and cognitive control. Nat. Rev. Neurosci. 1:59-65, 2000.

Miller EK, Cohen JD. An integrative theory of prefrontal cortex function. Annu. Rev. Neurosci. 24:167-202, 2001.

Paus T. Primate anterior cingulate cortex: where motor control, drive and cognition interface. Nat. Rev. Neurosci. 2:417-24, 2001.

Schall JD, Stuphorn V, Brown JW. Monitoring and control of action by the frontal lobes. Neuron 36:309-22, 2002.

Stuphorn V, Taylor TL, Schall JD. Performance monitoring by the supplementary eye field. Nature 408:857-60, 2000.

Week 5 (April 25):

Bichot NP, Schall JD. Effects of similarity and history on neural mechanisms of visual selection. Nat. Neurosci. 2:549-54, 1999.

Bichot NP, Thomson KG, Rao SC, Schall JD. Reliability of macaque frontal eye field neurons signaling saccade targets during visual search. J. Neurosci. 21:713-25, 2001.

Bruce CJ, Goldberg ME, Bushnell MC, Stanton GB. Primate frontal eye fields. II. Physiological and anatomical correlates of electrically evoked eye movements. J. Neurophysiol. 54:714-34, 1985.

Chelazzi L, Miller EK, Duncan J, Desimone R. A neural basis for visual search in inferior temporal cortex. Nature 363:345-7, 1993.

Gardner JL, Lisberger SG. Serial linkage of target selection for orienting and tracking eye movements. Nat. Neurosci. 5:892-9, 2002.

Gottlieb JP, Kusunoki M, Goldberg ME. The representation of visual salience in monkey parietal cortex. Nature 391:481-484, 1998.

Horwitz GD, Newsome WT. Separate signals for target selection and movement specifications in the superior colliculus. Science 284:1158-1161, 1999.

Moore T. Shape representations and visual guidance of saccadic eye movements. Science 285:1914-1917, 1999.

Ogawa T, Komatsu H. Target selection in area V4 during a multidimensional visual search task. J. Neurosci. 24:6371-6382, 2004.

Schall JD, Hanes DP. Neural basis of saccade target selection in frontal eye field during visual search. Nature 366:467-469, 1993.

Schall JD, Hanes DP, Thompson KG, King DJ. Saccade target selection in frontal eye field of macaque. I. Visual and premovement activation. J. Neurosci. 15:6905-6918, 1995.

Schiller PH, True SD, Conway JL. Effects of frontal eye field and superior colliculus ablations on eye movements. Science 206:590-2, 1979.

Tanaka M, Lisberger SG. Regulation of the gain of visually guided smooth-pursuit eye movements by frontal cortex. Nature 409:191-4, 2001.

Wurtz RH, Goldberg ME. Superior colliculus cell responses related to eye movements in awake monkeys. Science 171:82-4, 1971.

Worth Looking At:

Fischer B, Boch R. Peripheral attention versus central fixation: modulation of the visual activity of prelunate cortical cells of the rhesus monkey. Brain Res. 345:111-23, 1985.

Fischer B, Boch R. Selection of visual targets activates prelunate cortical cells in trained rhesus monkey. Exp. Brain Res. 41:431-3, 1981.

Moore T, Tolias AS, Schiller PH. Visual representations during saccadic eye movements. Proc. Natl. Acad. Sci. USA 95:8981-8984, 1998.

Wurtz RH, Goldberg ME, Robinson DL. Brain mechanisms of visual attention. Sci. Am. 246:124-35, 1982.

Week 6 (May 2):

Carrasco M, Penpeci-Talgar C, Eckstein M. Spatial covert attention increases contrast sensitivity across the CSF: support for signal enhancement. Vision Res. 40:1203-15, 2000.

Cavanaugh J, Wurtz RH. Subcortical modulation of attention counters change blindness. J. Neurosci. 24:11236-43, 2004.

Ignashchenkova A, Dicke PW, Haarmeier T, Thier P. Neuron-specific contribution of the superior colliculus to overt and covert shifts of attention. Nat. Neurosci. 7:56-64, 2004.

Kastner S, Pinsk MA, De Weerd P, Desimone R, Ungerleider LG. Increased activity in human visual cortex during directed attention in the absence of visual stimulation. Neuron 22:751-61, 1999.

Luck SJ, Chelazzi L, Hillyard SA, Desimone R. Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex. J. Neurophysiol 77:24-42, 1997.

McAdams CJ, Maunsell JH. Effects of attention on orientation-tuning functions of single neurons in macaque cortical area V4. J. Neurosci. 19:431-41, 1999.

Moore T, Armstrong KM, Fallah M. Visuomotor origins of covert spatial attention. Neuron 40:671-83, 2003.

Moore T, Fallah M. Microstimulation of the frontal eye field and its effects on covert spatial attention. J. Neurophysiol. 91:152-62, 2004.

Moran J, Desimone R. Selective attention gates visual processing in the extrastriate cortex. Science 229:782-4, 1985.

Motter BC. Neural correlates of attentive selection for color or luminance in extrastriate area V4. J. Neurosci. 14:2178-89, 1994.

Muller JR, Philiastides MG, Newsome WT. Microstimulation of the superior colliculus focuses attention without moving the eyes. Proc. Natl. Acad. Sci. USA 102:524-9, 2005.

Ress D, Backus BT, Heeger DJ. Activity in primary visual cortex predicts performance in a visual detection task. Nat. Neurosci. 3:940-5, 2000.

Reynolds JH, Chelazzi L. Attentional modulation of visual processing. Annu. Rev. Neurosci. 27:611-47, 2004.

Reynolds JH, Chelazzi L, Desimone R. Competitive mechanisms subserve attention in macaque areas V2 and V4. J. Neurosci. 19:1736-53, 1999.

Reynolds JH, Pasternak T, Desimone R. Attention increases sensitivity of V4 neurons. Neuron 26:703-14, 2000.

Sheliga BM, Riggio L, Rizzolatti G. Spatial attention and eye movements. Exp. Brain Res. 105:261-75, 1995.

Treue S, Maunsell JH. Attentional modulation of visual motion processing in cortical areas MT and MST. Nature 382:539-41, 1996.

Worth Looking At:

Bushnell MC, Goldberg ME, Robinson DL. Behavioral enhancement of visual responses in monkey cerebral cortex.I. Modulation in posterior parietal cortex related to selective visual attention. J. Neurophysiol. 46:755-72, 1981.

Corbetta M, Akbudak E, Conturo TE, Snyder AZ, Ollinger JM, Drury HA, Linenweber MR, Petersen SE, Raichle ME, Van Essen DC, Shulman GL. A common network of functional areas for attention and eye movement. Neuron 21:761-73, 1998.

Ferrier D. Cerebral localisation. (London, Smith, Elder and Co.), 1890.

Helmholtz H, von Treatise on Physiological Optics, Volume 2, translated by J.P.L. Southall (New York, New York Dover), 1866/1962.

Hoffman JE, Subramaniam B. The role of visual attention in saccadic eye movements. Percept. Psychophys. 57:787-95, 1995.

Kowler E, Anderson E, Dosher B, Blaser E. The role of attention in the programming of saccades. Vision Res. 35:1897-1916, 1995.

Mountcastle VB, Motter BC, Steinmetz MA, Sestokas AK. Common and differential effects of attentive fixation on the excitability of parietal and prestriate (V4) cortical visual neurons in the macaque monkey. J. Neurosci. 7:2239-55, 1987.

Posner MI. Orienting of attention. Q J Exp. Psychol. 32:3-25, 1980.

Week 7 (May 9):

Ditterich J, Mazurek ME, Shadlen MN. Microstimulation of visual cortex affects the speed of perceptual decisions. Nat. Neurosci. 6:891-8, 2003.

Gold JI, Shadlen MN. Representation of a perceptual decision in developing oculomotor commands. Nature 404:390-394, 2000.

Heekeren HR, Marrett S, Bandettini PA, Ungerleider LG. A general mechanism for perceptual decision-making in the human brain. Nature 431:859-862, 2004.

Horwitz GD, Batista AP, Newsome WT. Representation of an abstract perceptual decision in macaque superior colliculus. J. Neurophysiol. 91:2281-2296, 2004.

Horwitz GD, Newsome WT. Target selection for saccadic eye movements: prelude activity in the superior colliculus during a direction discrimination task. J. Neurophysiol. 86:2543-2558, 2001.

Horwitz GD, Newsome WT. Separate signals for target selection and movement specification in the superior colliculus. Science 284:158-161, 1999.

Horwitz GD, Newsome WT. Target selection for saccadic eye movements: prelude activity in the superior colliculus during a direction discrimination task. J. Neurophysiol. 86:2543-2558, 2001.

Kim JN, Shadlen MN. Neural correlates of a decision in the dorsolateral prefrontal cortex of the macaque. Nat. Neurosci. 2:176-85, 1999.

Mazurek ME, Roitman JD, Ditterich J, Shadlen MN. A role for neural integrators in perceptual decision making. Cereb. Cortex 13:1257-69, 2003.

Newsome WT, Shadlen MN, Zohary E, Britten KH, Movshon JA. Visual motion: linking neuronal activity to psychophysical performance. In: The Cognitive Neurosciences, MS Gazzaniga (Ed.), MIT Press, Cambridge. 1995.

Schall JD. Neural correlates of decision processes: neural and mental chronometry. Curr. Opin. Neurobiol. 13:182-186, 2003.

Shadlen MN, Newsome WT. Motion perception: seeing and deciding. Proc. Natl. Acad. Sci. USA 93:628-633, 1996.

Shadlen MN, Newsome WT. Neural basis of a perceptual decision in the parietal cortex (Area LIP) of the rhesus monkey. J. Neurophysiol. 86:1916-1936, 2001.

Week 8 (May 16):

Bechara A, Tranel D, Damasio H, Damasio AR. Deciding advantageously before knowing the advantageous strategy. Science 275:1293, 1997.

Berridge KC, Robinson TE. Parsing Reward. Trends Neurosci. 26:507, 2003.

Dayan P, Balleine BW. Reward, motivation, and reinforcement learning. Neuron 36:285, 2002.

Glimcher P. The neurobiology of visual-saccadic decision making. Annu. Rev. Neurosci. 26:133, 2003.

Holt CA, Roth AE. The Nash equilibrium: a perspective. Proc. Natl Acad. Sci. USA 101:3999, 2004.

Kahneman D. Maps of bounded rationality: a perspective on intuitive judgment and choice. In: Les Prixz Nobel 2002 (Ed. T. Frangsmyr) 416, 2002.

Maunsell JH. Neuronal representations of cognitive state: reward of attention? Trends Cogn. Sci. 8:261, 2004.

McClure SM, Laibson DI, Loewenstein G, Cohen JD. Separate neural systems value immediate and delayed monetary rewards. Science 306:503-507, 2004.

Montague PR, Berns GS. Neural economics and the biological substrates of valuation. Neuron 36:265, 2002.

Nash JF. Equilibrium points in n-person games. Proc. Natl. Acad. Sci. USA 36:48, 1950.

Rolls ET. The orbitofrontal cortex and reward. Cerebral Cortex 10:284, 2000.

Schultz W. Neural coding of basic reward terms of animal learning, theory, game theory, microeconomics and behavioral ecology. Curr. Opin. Neurobiol. 14:139, 2004.

Shizgal P. Neural basis of utility estimation. Cur.Opin. Neurobiol. 7:198, 1997.

Tremblay L, Schultz W. Relative reward preference in primate orbitofrontal cortex. Nature 398:704, 1999.

Week 9 (May 23):

Andersen RA, Essick GK, Siegel RM. Encoding of spatial location by posterior parietal neurons. Science 2230:456-8, 1985.

Andersen RA, Snyder LH, Bradley DC, Xing J. Multimodal representation of space in the posterior parietal cortex and its use in planning movements. Annu. Rev. Neurosci. 20:303-30, 1997.

Batista AP, Buneo CA, Snyder LH, Andersen RA. Reach plans in eye-centered coordinates. Science 285:257-60, 1999.

Brotchie PR, Andersen RA, Snyder LH, Goodman SJ. Head position signals used by parietal neurons to encode locations of visual stimuli. Nature 375:232-5, 1995.

Cooke DF, Graziano MS. Super-flinchers and nerves of steel: defensive movements altered by chemical manipulation of a cortical motor area. Neuron 43:585-93, 2004.

Graziano MS. Is reaching eye-centered, body-centered, hand-centered or a combination? Rev. Neurosci. 12:175-85, 2001.

Graziano MS, Reiss LA, Gross CG. A neuronal representation of the location of nearby sounds. Nature 397:428-30, 1999.

Graziano MSA, Hu X, Gross CG. Visuospatial properties of ventral premotor cortex. J. Neurophysiol. 77:2268-2292, 1997.

Grunewald A, Linden JF, Andersen RA. Responses to auditory stimuli in macaque lateral intraparietal area. I. Effects of training. J. Neuropysiol. 82:330-42, 1999.

Jay MF, Sparks DL. Auditory receptive fields in primate superior colliculus shift with changes in eye position. Nature 309:345-7, 1984.

Linden JF, Grunewald A, Andersen RA. Responses to auditory stimuli in macaque lateral intraparietal area. II. Behavioral modulation. J. Neurophysio. 82:343-58, 1999.

Mays LE, Sparks DL. Saccades are spatially, not retinocentrically coded. Science 208:1163-5, 1980.

Murata A, Gallese V, Luppino G, Kaseda M, Sakata H. Selectivity for the shape, size and orientation of objects for grasping in neurons of monkeys parietal area AIP. J. Neurophysiol. 83:2580-601, 2000.

Rizzolatti G, Scandolara C, Matelli M, Gentilucci M. Afferent properties of periarcuate neurons in macaque monkeys. II. Visual responses. Behav. Brain Res. 2(2):147-63, 1981.

Snyder LH, Batista AP, Andersen RA. Coding of intention in the posterior parietal cortex. Nature 386:167-70, 1997.

Snyder LH, Grieve KL, Brotchie P, Andersen RA. Separate body-and world-referenced representations of visual space in parietal cortex. Nature 394:887-91, 1998.

Toth LJ, Assad JA. Dynamic coding of behaviorally relevant stimuli in parietal cortex. Nature 415:165-8, 2002.

Week 10 (May 30):

Brody CD, Hernandez A, Zainos A, Romo R. Timing and neural encoding of somatosensory parametric working memory in macaque prefrontal cortex. Cerebral Cortex 13:1196-1207, 2003.

Hernandez A, Zainos A, Romo R. Temporal evolution of a decision-making process in medial premotor cortex. Neuron 33: 959-972, 2002.

Mountcastle VB. Central nervous mechanisms in mechanoreceptive sensibility. In: Handbook of Physiology: The Nervous System, Sensory Processes, Vol 3, Part 2, pp. 789-878. Ed. Geiger, SR. Am Physiol. Soc., Bethesda, MD. 1984.

Mountcastle VB, LaMotte RH and Carli G. Detection thresholds for stimuli in humans and monkeys: Comparison with threshold events in mechanoreceptive afferent nerve fibers innervating the monkey hand. J. Neurophysiol. 35:122-36, 1972.

Mountcastle, VB, Steinmetz MA, Romo R. Frequency discrimination in the sense of flutter: psychophysical measurements correlated with postcentral events in behaving monkeys. J. Neurosci. 10:3032-3044, 1990.

Mountcastle VB, Talbot WH, Sakata H, Hyvarinen J. Cortical neuronal mechanisms in flutter-vibration studied in unanaesthetized monkeys: neuronal periodicity and frequency discrimination. J. Neurophysiol. 32:452-84, 1969.

Romo R, Hernandez A, Zainos A. Neuronal correlates of a perceptual decision in ventral premotor cortex. Neuron 41: 165-173, 2004.

Romo R, Hernandez A, Zainos A, Lemus L, Brody C. Neuronal correlates of decision making in secondary somatosensory cortex. Nature Neuroscience 5:1217-1225, 2002.

Salinas E, Hernandez A, Zainos A, Romo R. Periodicity and firing rate as candidate neural codes for the frequency of vibrotactile stimuli. J. Neurosci. 20:5503-5515, 2000.

Romo R, Salinas E. Touch and go: decision-making mechanisms in somatosensation. Annu. Rev. Neurosci. 24:107-37, 2001.

Salinas E, Romo R. Conversion of sensory signals into motor commands in primary motor cortex. J. Neurosci. 18:499-511, 1998.

Romo R, Hernandez A, Zainos A, Salinas E. Somatosensory discrimination based on cortical microstimulation. Nature 392:387-390, 1998.

Werner G, Mountcastle VB. The variability of central neural activity in a sensory system, and its implications for the central reflection of sensory events. J. Neurophysiol. 26:958-977. 1963.