Pigeon nidopallium caudolaterale, entopallium, and mesopallium ventrolaterale neural responses during categorisation of Monet and Picasso paintings

Abstract

Pigeons can successfully discriminate between sets of Picasso and Monet paintings. We recorded from three pallial brain areas: the nidopallium caudolaterale (NCL), an analogue of mammalian prefrontal cortex; the entopallium (ENTO), an intermediary visual area similar to primate extrastriate cortex; and the mesopallium ventrolaterale (MVL), a higher-order visual area similar to primate higher-order extrastriate cortex, while pigeons performed an S+/S- Picasso versus Monet discrimination task. In NCL, we found that activity reflected reward-driven categorisation, with a strong left-hemisphere dominance. In ENTO, we found that activity reflected stimulus-driven categorisation, also with a strong left-hemisphere dominance. Finally, in MVL, we found that activity reflected stimulus-driven categorisation, but no hemispheric differences were apparent. We argue that while NCL and ENTO primarily use reward and stimulus information, respectively, to discriminate Picasso and Monet paintings, both areas are also capable of integrating the other type of information during categorisation. We also argue that MVL functions similarly to ENTO in that it uses stimulus information to discriminate paintings, although not in an identical way. The current study adds some preliminary evidence to previous literature which emphasises visual lateralisation during discrimination learning in pigeons.

Figure 1

The sequence of events during an S+ trial (a) and an S− trial (b). Both trials began with a 5000 ms intertrial interval (ITI), followed by the ready period in which a black dot appeared on the screen. After pecking the dot three times, the pause period was initiated in which the birds were required to refrain from pecking for at least 1000 ms. Following the pause period, one of the 14 painting stimuli appeared for a minimum of 5000 ms, during which time pecks were recorded. If an S+ stimulus was displayed, the birds were rewarded following the first peck after 5000 ms, and the stimulus turned off. If an S− stimulus was displayed, they were required to wait 5000 ms until the stimulus disappeared automatically, and were not rewarded. Wheat reward was delivered by a food hopper for 2000 ms on S+ trials, and S− trials had a matching 2000 ms period with no reward. M, Monet painting; P, Picasso painting.

Figure 2

The electrode track reconstruction. (a) NCL. Solid red line—C3; dashed red line—B2; solid blue line—B9; dashed blue line—C8. (b) ENTO. Solid red line—C4; dashed red line—B10; solid blue line—B11; dashed blue line—B5. (c) MVL. Solid red line—D12; dashed red line—D10; solid blue line—D14; dashed blue line—D11. Brain regions (as defined by Reiner et al.): A, arcopallium; CDL, area corticoidea dorsolateralis; DA, tractus dorso-arcopallialis; E, entopallium; HA, hyperpallium apicale; HD, hyperpallium densocellulare; GP, globus pallidus; M, mesopallium; MV, mesopallium ventrale; MVL, mesopallium ventrolaterale; N, nidopallium; NCL, nidopallium caudolaterale; Rt, nucleus rotundus; StM, striatum mediale; TeO, tectum opticum.

Figure 3

Behavioural performance. Overall behavioural performance on the S+/S− discrimination, as indicated by the discrimination ratio (DR). The dashed line denotes chance performance (0.5), and error bars are ±1 SEM. M+, Monet S+; P+, Picasso S+.

Figure 4

Overall population profiles. The overall population profiles for (a) NCL, (b) ENTO, and (c) MVL. Neuronal data was normalised against the maximum firing rate during the ITI, and bin width is 50 ms. Vertical lines separate the different periods of the task. Shaded bands represent ±1 SEM. ITI, intertrial interval. *p < .02; **p < .01; ***p < .001.

Figure 5

Hemispheric population profiles. The population profiles for left (a) and right (b) hemisphere NCL, left (c) and right (d) hemisphere ENTO, and left (e) and right (f) hemisphere MVL. Neuronal data was normalised against the maximum firing rate during the ITI, and bin width is 50 ms. Vertical lines separate the different periods of the task. Shaded bands represent ± 1 SEM. ITI, intertrial interval. Black asterisks represent significant S+S− differences that are the same across hemispheres, purple asterisks represent significant S+S− differences that are specific to one hemisphere. *p < .02; **p < .01; ***p < .001.